I tried locksmiths and one of those key machines found in Walmart.
I would like to make a duplicate.
I think the tricky part would be that "groove" that runs about 3/4 ths of the way.
If it's a commercially made padlock other than the "Master" brand that are built from laminated sheets, it should be possible to get a key blank that fits the keyway, from which you can cut a matching key on any key duplicator. You might have to get it from the manufacturer, though, and if the lock was very cheap matching key blanks may not be available.
With the bitting on that key, however, it's just a warded lock, rather than a pin tumbler type, and a key cut on the same blank with just the tip left at full height (that is, all the rest of the shank cut as deeply as the cuts you have) would act as a "master key". I wouldn't expect that lock to protect anything, and I wouldn't worry about trying to duplicate the key you have. Instead, spend your money getting a padlock with an actual pin tumbler mechanism that at least requires more than a file and basic knowledge of locks to master key.
Many years ago (1970s) I made a duplicate key from the plastic of a three-ring binder cover. I just traced the key, cut the portion that was above the first ridge in the keyway (so the flat section would work), and cut it very carefully to shape with scissors. To use it, I'd slip it into the lock, where it would push the tumblers to their cut points, then I'd twist the cylinder with a screwdriver, knife point, or other similar tool (what locksmiths call a "torque bar").
This won't work with the lock you have, because it's not a tumbler type lock. Your lock is a warded lock, and depends on the very tip of the key applying the torque inside the lock, while the bitted portion simply has to be cut away to pass the "wards" inside the lock that prevent wrong keys from turning (this works like the old skeleton key locks that were common on houses before 1900, and on interior doors into the mid-20th century).
To duplicate this key, then, you need a full length blank that's strong and stiff enough to turn the lock mechanism. An aluminum, steel, or brass/bronze key blank would do the job, but very cheap locks aren't generally supported by key duplication services or locksmiths, because it's cheaper to replace the lock than to duplicate a key, and there's not enough demand for duplicates to make it cost-effective to stock blanks (never mind that a common key duplicator can't cut the straight-sided bitting on your existing key).
Bottom line, if you can't buy key blanks or duplicate keys from the lock manufacturer, you can't make extra keys that will work in this kind of lock, even by "unofficial locksmith" methods. You can't even pick this lock with the methods commonly used on tumbler type locks (rake and torque bar), because the torque must be applied at the tip of the key.
Your time and money would be better spent obtaining a quality padlock for which key blanks are available (and which will come with two keys, sometimes more), and duplicating one of those keys as many times as needed, then putting the lock on a metal box instead of a plastic one that anyone with a screwdriver can break into, lock or no lock.
When I lived in Kathmandu, Nepal, for some months, I also had to get a key for a padlock duplicated. And the way it was done there will certainly count as a lifehack here :)
So I found this tiny workshop specialized on duplicating keys, just maybe 1.2×3 m in size and located right here. There was a friendly old man inside. I gave him the original key, and then within 5 minutes, to my astonishment he did this:
He looked through a box of all kinds of old and unused keys until he found one suitable to serve as a blank for mine. Which means, it had to have more material in all places than mine, allowing to cut mine out of it.
In your case it will be enough to find an old key that has enough material in the tip section only, as your padlock is just a warded lock as Zeiss Ikon remarked. If there is material missing in the other parts, it will not hinder the function of the key.
He carefully clamped the original and the blank key in parallel into a vice clamp so that they were perfectly aligned.
He used several small files and the blade of a metal saw to cut down the blank to the shape of the original, without ever touching the original.
He charged me just 70 Rupees for the service (about 0.70 USD at the time).
The duplicate worked! The only caveat is that this technique is a bit less exact than with a duplicator machine. So when duplicating from what is already a copy of an original key, it may not work well at first and may need some adjustments by trying it on the lock. (So when you need a key duplicate in Nepal, the trick is to bring the whole padlock in this case!)
High-Tek, High-cost, difficult to manufacture lock hack.
To make another duplicate key, you will need a key blank to fit the profile of the lock you own.
Without that blank, your efforts are futile. You can buy one. (This does not need a lifehack.) You can make one if you refuse to purchase anything. (This does not need a lifehack.)
To make a key blank to fit the lock you own: (This does not need a lifehack)
Contact a tool and die machine shop by telephone directory listings for your city. They can and will make an exact copy on their milling machine. Tool and die shops work by quotes so you will have to visit them and have the estimator give you an estimate and to schedule your job. Set aside US$300 to US$500 for up to two hours of production time and tool stock.
While it is possible to make the blank on a lathe, it is much more difficult as it is made for turning rather than milling. Your machine time will increase and you'll need an experienced lathe operator for this. In effect, you are doing milling on a lathe—Not the best tool for the job.
If you choose to make a mold of the key using something such as the lost wax process, you are limited to metals with a relatively low melting point such as bronze or copper which unless case hardened or chrome electroplate are relatively soft and distort easily. In this case, you would make a mold in soap as directed by Edward. Fill the void with wax. Make a mold of the wax with sand. Bake the mold to melt the wax. Fill the hole left by the wax in the sand with molten metal. Let cool. Break away the sand leaving you with a mold of the key. File the key duplicate wells off to get a clean, smooth surface on your duplicate key.
You might have to do this a few times until you get the technique down pat. By then, you'll have a new skill.
Good luck !
Press the key into modeling clay to form a mold removing the key once pressed. Then using melted lead, very low melting point and can be done on any source of heat, pour into the mold you just made. Once cooled it may need some sanding, but lead is super soft and will sand easily. Normally sand is used for creating molds for the molten lead but your item is too small to use sand.
Hold the teeth on one side of the key over an open flame until they are sooty. Use a lighter or a lit candle. Move the teeth of the key back and forth over the flame. It should take around 1 or 2 minutes to blacken one side of the key. Once the key is charred on one side, set it down until it is cool to the touch.
Use a pair of pliers to hold the key so you don’t burn your fingers.
Stick a piece of clear tape on the blackened side of the key. Cut a piece of clear tape the same length as the key. Standard sized clear tape should work for most house keys. Carefully lay it on top of the key so it doesn’t crease. Press the tape firmly onto the blackened side of the key so the char transfers.
The outline of the key will transfer to the sticky side of the tape.
Leave a fingertip-sized bit of tape at the end of the key so it’s easier to remove.
Remove the tape slowly after 10 seconds. Peel the tape back, being sure that it doesn’t fold or crease. The char will leave residue on the sticky side of the tape in the same shape as the key.
Use rubbing alcohol to remove any residual soot from the key.
Place the tape on an expired credit card or plastic gift card. A standard thickness card will work best. Stick the tape so the entire imprint of the key is on the card. Make sure the tape lays flat so the shape of the teeth is not distorted.
Be sure to place the tape away from any raised letters or numbers on the card otherwise it will be too thick to fit in the lock.
Use a light-colored card so you can easily see the imprint of the key.
Cut out the shape of the key with a pair of scissors. Carefully maneuver around the outline of the key. Be mindful around the teeth, being sure to cut directly on the outline. If the teeth are not close to the correct size, they will not be able to turn the lock.
It doesn’t matter how the large end of the key is shaped. As long as the teeth are cut correctly, the key should work.
Hold the original key up to the one you’re cutting out to compare the teeth.
Turn the makeshift key slowly in the lock. Insert the key delicately into the lock so it doesn’t bend or deform. Once it’s fully inserted, hold the key as close to the lock as you can and turn it. It should unlock easily.
Don’t force the key to turn or else it may bend or break.
Low-Tek, low-cost, easily replaceable lock hack
After examining your question and comments more carefully, I suggest that until you can afford to replace the one-key lock for the plastic container on your bike, you can use simple plastic coated (or bare) wire twist-ties to hold the box hasp closed. They will be very secure from accidental opening and easy to use, re-use, and replace after they wear out.
So far as tamper-free security, you don't want to leave anything you value in such a container unless you are present. Obviously, if there's nothing left inside, there's nothing to lose.