What's the diameter of the nylon seat? I can't be that hard to make new ones out of hard rubber bars: Cut the right height, dremel the hole, bevel the side for the screw.
3mm inner hole
Estimates, dont have one on hand atm.
I considor myself rather good at making small bits like these, sadly, it will not work...
Anything made out of "softer" material effects how the gun/valve works. The WHOLE co2 pressure presses down on that small seal. When the hammer hits, it only opens up VERY little. Any softer material simply will not open the valve as the material soaks up all the force of the hammer.
Only way i see to make it somewhat usable without having to mod the gun is to make it work a bit like WE valve works. Wider area of contact and sealing. Sadly this needs quite a lot of work to the valve itself and WE parts will not fit, so all must be built by hand.
Sadly WE doesnt seem to make single-stack mags. The one im hoping to copy/convert to is a large mag.
...And im not even 100% sertain if it will work at all.