Reseal kit or info on 1 ring 4 RS1 please

I need the main air tube seal for my Evanix Rainstorm One .22. The large ring that goes in back of tube right where it meets the gauge block. My Altaros needs to be pulled & rebuilt after 7+ years. If I can get a full kit one of you can put together I'd gladly pay. I just don't have enough for shipping & full reseal of 2 rifles. One's down completely & this RS is not at full capacity.



I know of Mr. Piatt but just can't afford it right now. If I had the cash I'd send her to him with the Altaros kit & have him set it all up optimally. I will in the future but until then I figure just pull the reg, put in the one ring it needs, and test the new heavy .22's I have that someone gifted me. I can tell you they don't do well at 861fps. I need that reg out & full power. I may rebuild reg, or may have discovered a new hunting pellet for far range Groundhogs. Eventually I'll have every spring gun & PCP I dream of at night but not for awhile yet.



So exact diameter & best durometer for that back main seal on the air tube fellas & I can do that much myself. Help a Brother out? I'll gladly pay for the kit, your time, & shipping. 
 
For any that care, Mr. Piatt informed me that the O-ring in question is a M3x27 exactly, OEM factory spec. A SAE 213 may work. I'll try whatever I can find at ACE until I get what's needed from The O-ring store. Thanks Mr. Piatt.

If anyone knows of kits to rebuild my Altaros regulator, I'd appreciate it. Why don't I measure them when I take it out? I'll have to with calipers, micrometers, depth gauge I have; but O-rings more often than not come out distorted from the pressure on one side or both. An accurate on the nose reading won't be obtained. I guess I'll have to go by ID & channel depth but it's not easy as my Starrett gauge rods probably won't even fit in most of those tiny channels. 

I'd love to learn about durometers, compression, standards for gauging sizes. Does this change in CO2, 2K fill, 3K fill, 4350psi Big Bore fills, High Pressure Helium? I'm kind of thinking when you use Helium all you can hope for is your shots taken within a few hours, or do they hold month on end? Helium was originally used to check where HPA might leak, surfaces may not be true, etc. The guy just figured give it a try. Since it's 1 molecule, not 3, it's much thinner & simply slips through the O-rings itself, unless they're using special O-rings. Not unlike a virus is so small, condoms don't guarantee anything from viral, but are effective from bacterial or fertilization. Just a comparison.