iMac internal cd/dvd drive replacement

I live in Costa Rica, and have been a Mac fan for years. My iMac internal drive went out on me. I took the computer to an Apple repair place, and after checking it out they said it would have to be replaced. Only costs $225! Ouch

A Mac using friend told me he was sure I could put in a PC drive that would work, for about $30 to $50. I'm in the USA until Aug. 12. Where can I get one? preferably on line? If it's any use or an interesting challenge to anyone I'd be glad to donate the non functioning one to you.

Sincerely,
Bob Jeffery
gapjeff@gmail.com
(my email is in my wife's name, no let it give you a start)