Gah, you guys need to stop losing CD-Keys. I really don't understand how you do it...
Anyway, try scanning torrents or crack/serial sites. You might be able to find something that could potentially work. Either way, make sure you protect your computer if checking serial sites... scan for spyware when you're done. Type cracksearch in google, that should lead you in the right direction for those.
But, if you want to go legitimate, I'm not sure there's much of a way around it besides looking for your own key, or buying a new one. Maybe Blizzard could help, though I doubt it.