Buying prescription opiate pills from drug dealers is very expensive. I would keep a close watch on your bank accounts.
Also buying these drugs from dealers don't know what they are really being made from. They may look the same but many times they are not being made to the same standards as the pharmaceutical companies.
Due to the high expense of these pills off the streets its why so many once addicted move to much cheaper heroin.
If hes addicted to these pills chances are slim to none that he can stop on his own or as he says "working on it". It doesn't work that way.
Drug testing him wont stop it either. You already know he has a major problem.
Going to meetings & educating yourself is the right thing to do for you.