Oh, cheap mouse, never really did that. There's a Logitech keyboard/mouse combo deal you can sometimes find under $20, I've got 3 of those now for my Pis. K200 keyboard, mouse I can't read usually. It's optical, has a scroll wheel that acts as a third button but it's a little like standing on a rocking chair. Been buying and using them for over a year because they're USB, I still have PS/2 stuff too.
I love the cheap deals shipped direct from China. Aliexpress, eBay, Gearbest, dx.com, miniinthebox.com, futurelec. They take weeks to come in the mail so I constantly go to the mailbox hoping for surprises that I've forgotten about. Most under $5 though.