I've been a certified diver since 1987.  My work allowed me to travel to many places and my SCUBA gear was well used.  I'm a retired farmer but still get the itch to dive.  I have over 6 full sets of regulators.  We live in a small town with no dive shop.  This was not a real problem until lately.  The dive shop I used to get service kits has closed due to COVID.  Finding a new shop has been difficult.  Most of the shops I have visited only offer courses in OW/AOW/Nitrox.  I've got all those merit badges.  But I'm being told that only trained and certified service techs that are employed by a dive shop can rebuild regulators and order parts.  My state has a right to repair law and if this applies to John Deere tractors, I don't see how this would not apply to regulators.

This brings up two questions:

For older, certified divers, how do you start a new relationship with a dive shop?
How do you obtain service kits and repairs parts to maintain you regulators?

If shops are found to have sold service kits to individuals, their agreement will apparently be terminated. Who made your regs? There are folks on ScubaBoard who love to DIY. They can tell you if and where you can source service kits.  

Just walk into a shop? Where are you? Maybe we could recommend somewhere better.

So that type of contractual clause seems to violate PA's "right to repair law."    My regulators are a mix of US Divers (Aqualung), Scubapro, and Hollis.  I'm not really interested in complying with some of these dive shops policies (i.e. pay more than $300 for a $15 service kit, having some child incorrectly service/repair my regulator, or requiring an upgrade to a poppet for $400)

Doesn’t matter. That’s how the dive industry works. You can also mail your regs to shops that do mail order reg service. SB can provide recommendations.

You could go the mail order route, or if, and it seems you are willing, do it yourself.
I am not a farmer, but a bit of a redneck.  Service kits are a scam lol.  I have been servicing my own and family regs for about 20 yrs. Most regs share common service parts ie orings, seats etc.

I would keep a basic set that is the simplest and easiest to access parts.   A list or pics of what you have would help.

I service my own regulators.  It's a scam on the part of SCUBA shops.  

I have AquaLung regulators.  I found the specs and diagrams online.  I purchase the rebuild kits online.  They are very easy to rebuild.  If you aren't mechanically inclined, maybe it's scary.  However, if you have a little basic mechanical ability you can easily rebuild your own.

I've been doing my own regulator and tank valve rebuilds for more than 40 years. The parts are available online for the vast majority of regs and valves.

Their is nothing special about the o-rings unless they're used in oxygen-rich mixtures, then you should use o-rings that are oxygen rated.

The prices dive shops charge ought to be criminalized.

Depending on the age of your equipment, rebuild kids are readily available from a variety of sites. Vintage Double Hose, and Northeast Scuba Supply both come to mind. I had no problems sourcing parts for a Conshelf XIV which is now allegedly military/professional divers only