Ebay, Ebay, Ebay! Every few weeks an old atari control panel goes on auction on ebay. Just last week a trivial pursuit panel went for about 15 bucks. For those of you whoe don't know trivial pursuit had 4 of these buttons as well as two large illuminated pushbutons, the same ones that happ charges 3-7$ a piece for. There's probably a few panels out there that have these on them up for bid right now. I think I saw a complete pacman cocktail control panel. You would get two with it as well as an original pacman 4-way joystick.
Ebay is your friend and used parts are a good thing.