Lite-On, Keytronic, and Mitsumi are pretty good cheapies, IMO (...and I like tactile feedback, having an IBM Model M
).
If you ever need a used PC, you could try buying them with keybaords and mice. Retrobox, FI, gives a Quietkey with every Dell--easy way to get one, if you need such an old-but-in-good-shape PC (like for a firewall or small server of some kind).