Or you could do the environmentally friendly, correct, cheap, and easy thing and just charge it with the very easily available R134 and suffer the oh-so-slight loss of performance. My car only takes 2 minutes more to cool off than it did before the switch and I definately havn't died of heat exhaustion yet.

I don't like to argue about things quite so dumb, but here's my on-topic advice. Don't bother switching back to R12 if the system works and has already been switched to R134a. It will save you problems and headaches later. Plus, why fix something that isn't broken?