YES, you do
need to be certified and when this happened is when the price started to skyrocket. This happened around 8-9 years ago by the EPA. Even now you have to be certified for R-22 for home AC and the like but the whsl price is still under $50 for a 30lb. jug. I bought a 30lb. jug of R-12 just before the certification was needed and paid $194 at the time which now is a steal, and still have about 25lbs left.
NO, it's not for sale!!
Every now and then I see a jug of R-12 advertised in our local paper by an individual and asking near $800. I've heard there is someone near here who has a basement full of the stuff but don't know who.
Good luck in your search or changeover to R-134a!!