You can already buy some refrigerants legally without any license, and somewhat amusingly (or sadly), even contribute to global warming by releasing as much of it into the atmosphere as you want! It's not marketed as a refrigerant, because that would make the EPA regulate it, but of course the chemical itself doesn't care about such trivialities and will cool the same when it evaporates. If you want to go down a rabbithole, search for "duster spray AC recharge".