Here are two places I get parts if needed.
http://www.vintagescubasupply.com/
http://www.vintagedoublehose.com/
there are some other sites to get parts but these have more than most.
Honestly my DA Aqua-Master still has all its original parts except a diaphragm and inlet outlet disk. I have service kits and it is still an easy breathing reliable regulator. I have two others and they were salvage jobs and I brought them back to life. Hated to see them just get thrown away. Now they are worth more than 5-6 times what they were new.
We figured that it was a liability issue but when we discussed it with him it boiled down to he was just stupid. His boat is just a platform. They do not guide just drop you off and pick you up. They have no agency liability and it says so on the release form. He just happens to be a DM. Funny thing he was doing his instructor cert for PADI and failed. Now I can see how. The other thing is Carlos who owns a dive shop had been taking students and tourists out on this guys boat and he was sooo pissed off he will never use him again.
Cave diving well you hit it on the head do what that bunch says or hit the road. They do seem to be adverse to open discussion. I do technical diving, deep, wreck, etc etc but never wanted to do Caves. I just did not like the odds and the mindset of most of them turned me off.