Try the Apple store
If you live near an Apple store, or even just an Apple authorized repair centre, drag the MBP down there, when its not busy, and ask politely. It certainly can't hurt, and if the repair/replacement is not to difficult you may end up being the victim of good customer service. I think I read in a different thread, somewhere, that Apple stores keep a supply of used keys from repairs. I know when I lost a rubber foot off of an iBook, they were more than happy to give half a dozen replacements. Show up in person, on the telephone you are more likely to get the "official" answer. In person, most people will try to be accommodating.
Good Luck.