Steal the feet off of one of your wife's kitchen appliances. Bet you have some old pc of junk ready for the garbage...or a old style hardware store for some rubber feet/rubber bumpers.
Preferably the little rural type hardware store that will sell 1 or 2 for 8 cents each rather than a package of 200.
Actually, just measured for the heck of it. The missing bumper is the same thickness and just about the same diameter as a standard rubber spacer used for spacing peg board...so, a little recess trim cut, a small bolt and nut and away you go. Or glue.