Look for a used Cherry G80-3000 and that's anything you'll ever need.
You could also try the IBM model M, I like my M2 even better because of it's small size and buckling springs. If you could not find one, try Unicomps.
Anyway, you should find what you're looking for around here, look in great finds and marketplace, or ask IRC. I don't think you'll need to look ebay.