I bought R-12 on ebay - it's selling high right now ($20-$30 per can), but if you purchase higher quantities or wait until the off-season you should be able to get it for around $15/can. Still high, but for now I'd rather keep it an R-12 system than convert it to R-134. Given that the e30 holds 2 pounds (less than 3 cans), it's not that bad if you do it yourself. I found an older R-12 reclaimer from a service station; it was very inexpensive and it makes it possible for me to open up my own systems.

You need to be EPA certified to purchase R-12, unless you verify that you are buying it for resale. I got my EPA certification online for $20 I think, and actually learned a few things getting ready for the test. I can send you the link if you are interested.

-jrm