My grandparents bought 3M's Splash Goggles to try to prevent SARS-CoV-2 entering their eyes, for they can't find any store that sells full face respirators to individuals , not even Amazon! They're stunned that 3M hasn't accompanied it with a case to store them. They're afraid of buying one off Amazon.com, because they don't know if a case by some random manufacturer is big enough to contain these Splash Goggles. They can't find any open retailer in Canada that sells them.
Your grandparents can relax their relentless search for a specific storage case.
HACK: Find a zip-lock plastic bag big enough to hold your grandparents' goggles. This will be sufficient to protect the eyewear from all but a direct meteor strike. They are clean and dust resistant so long as the seal remains closed. They won't scratch the goggles lens.
You can find the size by comparing the length of the goggles to the length of the box of zip-lock bags. They're available in most any grocery store convenient to where
you they live.
When you want another storage case, pull another one out of the box. The bags are made by a variety of different manufacturers and in different thicknesses. Use one bag per pair of goggles to make handling more manageable.
If it's about protecting the goggles from scratches, your grandma can knit a fluffy drawstring bag for them. I suggest using either thick yarn or a very thick pattern like patent or cabe knit. This is a good way to use some leftover yarn and it adds a lovely personal touch to this otherwise grim situation.
I've kept my phone in a drawstring bag knit from plushy sock yarn for several years and there's not a single scratch on the display. And you can use the bag to wipe the phone/goggles clean.
Instead of buying a dedicated glasses case for the goggles, you/they can buy any box which is big enough and not overly big. I would start looking at the freezer and lunch box section of the shops.
Such a box is likely to be overly big, fill the extra space with kitchen paper or a piece of cloth which can be replaced at each use or which can be cleaned.
If they prefer to buy online they can go by the measurements of the box as given and the measurements of the googles, as measured by themselves. I would prefer to buy from a shop where you can check out the shape and quality of the box.