If you are tight on cash I recommend you make a post on the buy/sell/trade section of shoryuken.com and ask if anyone wants to sell some buttons from a Hori Real Arcade Pro joystick.
The Real Arcade Pro, or HRAP as it is called comes stock with generic Hori buttons, but the SF players take them out and replace them with Sanwa or Seimitsu. They usually just keep the old buttons for back ups.
The Hori buttons are nice, just not quite as sensitive as a sanwa, and they fit the exact same hole.
You could probaby get one of the vendors on there to sell you a couple of Seimitsu joysticks, which are cheaper than Sanwas, but still high quality, and some Hori buttons together as a deal. I would not pay over 50 cents each, though.
You might even want to ask the guys at lizardlick.com if they can do that for you.
@HarumaN: That's unfortunate, he was always a real nice guy to deal with.