If you don't learn to do stuff like this yourself, it could be a real challenge to find someone to do it, and it could be very expensive'
I been plumbing Cat heaters in RV for many years, and I know what works.
The very first one in 1975, I plumbed w/ autoparts fuel line hose, never a problem. The later ones, including 2 Cats in my current RV, I plumbed w/ clear vinyl hose from Ace hardware. Either type hose is indestructible by propane, and will handle 10x the pressure, Anymore, I even use good quality zip ties for all clamps. Venting ?? Do what you think you have to do, but I don't even think about venting. But one thing is for sure, if I thought I had to leave 4 windows and 2 vents cracked, I'd dump the Cat heater first !
But getting back to OP question, keep looking.