from my reading you need a license to buy Freeze-12 (could be wrong) I've been looking into eviro-safe's R-134a R12 Sub Alternate A/C Recharge Kit. It says it's compatible, and from the people that have used it they say it works well. There is some concern about it's safety, being it's a hydrocarbonate (i think)
r-12 is still around and is better than r-134a, but it's rare that a shop will still do the re-charge due to the EPA and penalties.
I'm thinking of going the
enviro-safe route. $35 for a full kit including fittings, gauges, and a leak stopper.