Cheap Sanwa Screw in Buttons $2.25 each see link. Sanwa sticks also available.

over at Arcadecontrols.com You get get cheap Sanwa parts. He only sells screw-ins, but for $2.25 you can't beat it. He also sells Sanwa sticks for $18.95. And his Happ stuff is cheap to.
The seller goes by Ponyboy.
http://forum.arcadecontrols.com/index.php?topic=36770.0