Replacement keyboard keys?

I think the only thing you could do would get your hands on a dead keyboard and slaughter that.

 

Try http://www.laptopkey.com/

Seems expensive for what you're getting, but cheaper than replacing the entire keyboard.

Be sure you haven't broken the actual connection tabs on they keyboard itself otherwise new keys aren't going to stay/work properly. If that's the case, you're likely looking at replacing the entire keyboard.