Thankfully R12 is still pretty available at places like Craigslist. You used to be able to get it on eBay but that ended earlier this year due to a change in eBay policy.
Gotta be mindful of purity in those instances. I’d rather source mine from reputable outlets. Course, it doesn’t hurt to have a fairly reliable source. Funny thing, you can still purchase it from south of the border due to their third world status. Go figure.
I suppose the upside is we’re rapidly approaching third world status so R12 should be available and affordable before too long.