looking for a first stage...

[T210RVR]

They had the same first stage NIB on Ebay for $59.00 plus shipping.

 

[halocline]

why could you not use a 3/8 to 9/16 adapter with a qd screwed into that. this prevents all the hoses from pressurizing this leaves just the first stage with pressure on it bleeding thru a flow restrictor to the 02 analyzer, so it takes what 2 seconds to bleed off?

here is a similar system with no bleeder valve

I think I understand what you're thinking about. Not having a HP hose attaches is what results in much less gas loss/time bleeding to de-pressurize the reg.

All the O2 analyzers I've used (not many) have the LP inflator hose attachment, which I guess you could easily mount on the 1st stage with adapters and no hose. But, a short inflator hose might be a little more convenient to connect to, you can move it around easily with the reg in place.