It sounds like what you want is an anti-fatigue mat, typically used by chefs or factory workers, who often have jobs that require being on your feet most (if not all) of a work shift.
You will want a mat made with gel or foam. These typically come in half-inch dimensions, though you may be able to find something thicker if you purchase via a more industrial supplier/source.
Option #1 Not sure of your location and what is accessible, but the quickest and easiest (and possibly least expensive) would be to go to your local Walmart, Sears, Lowes or Home Depot ... or other department- or home goods-type store ... and go to the section where they have the floor mats. You may see outdoor and kitchen floor mats in the same section; the kitchen type are your best bet, as these are designed for with those standing in one place for a long time (as in washing dishes) in mind. Look for the thicker variety, typically made with some kind of foam or gel material. Try them out right there in the store and pick the one that makes your feet say "ahhhh!".
Option #2 You could also try some of these suggestions, offered as examples of different types, material/construction, and pricing:
- Better Homes and Gardens ProChef Comfort Chef Mat available at walmart.com
- the "original gel-filled comfort mat"available at gelpro.com
- anti-fatigue mats, runners, and other options available at globalindustrial.com and floormatcompany.com
- rubbercal.com
- sears.com
- Royal Anti-Fatigue Comfort Mat available at amazon.com
Option #3 You may also want to consider foot orthotics, such as is available through places like the Good Feet Store (goodfeet.com), for proper arch support - critical for those who's daily activity require or involve being on your feet for extended periods of time.
Hope this is helpful!