A:Answer Insignia Support replied and they don't have replacement feet. After some trial and error I did find one that is a reasonable replacement.
UXcell 50pcs Silicone Rubber Round Snap-in Locking Hole Stoppers, Waterproof Hole Plugs for 6-7mm Metal Tube, Furniture End Caps Inserts, Black
It takes some pressure and wiggling to get it in, but once instead it's secure and provides the needed grip to prevent the stand from sliding.
Hope this helps others who have been previously "de-feeted" ;-)
