As far as I can recall, most companies in the US were tighter than a frog's ass about their service kits and spare parts falling into the hands of the public -- ScubaPro, chief among them, tied as they once were, to some Byzantine "lifetime warranty" agreement, that few living now seem to understand.
Poseidon came in a close second, with a host of idiotic US distributors -- yes, Parkway, I'm thinking of you. Dealers couldn't even get service kits for a period of time (some shortage of teflon and rubber bands?); and we were flipping diaphragms, reusing sintered filters and HP seats, and scavenging o-rings for our own gear.
The wider DIY element is fairly new to the US, even though Harlow's grassroots repair manual was around as early as 1999 -- and he even covered those difficulties in obtaining OEM parts at the time. I was only able to obtain kits, from a shop where I had once worked -- and even then, passing the kits along was treated almost as illicitly as a drug deal, a small brown bag slid across a counter along with a cash exchange.
Now, there's a retail market for a number of manufacturers -- a real positive change that ScubaPro could eventually embrace, should they ever decide to leave the trees . . .