Where to find steel footers?

parts-express(dot)com

Stillpoints Ultra SS Footers.

Cheap as can be is to buy some ordinary ball bearings, and use a cheap steel washer under to keep the ball bearings in place

My being a natural cheapskate helps...
An alternate would be various other materials for the small washer.
Nearly endless possibilites.
Different size bearings..
Nylon washer,
Bronze washer,
Fiber washer,
Neoprene washer,
magnetized top washer to stick on base of equipment,
Cut a hole in a refrigerator magnet sticker for base of equipment..
Like I said, nearly endless possiblities

Try a hardware store. They often carry small brass or stainless steel tack like hardware which is rounded on one side and has a nail on ther side that you can push or lightly hamer into the underside of a floor standing speaker. Just use three in a triangle so you dont have to worry about leveling if your floors are basically level to start with.