I don't know where to find any impervious to the new gas yet but I have repaired vintage diaphrams which could not be found by rubbing a silicon sealant into the fabric, let it dry and it worked fine. There may be better solutions, chemicals gasket sealers, rubber cement etc. that will handle the new gas that you may be able to rub or spray on before installing, but it worked for me.I also have an old car jack that that I picked up at a yard sale, beafier and a higher lift than anything you can buy now, when I got it it leaked and I tried to find a kit for it or match a braky cylinder rubber to it, If I remember correctly the original was leather, in any case none were to be found and the hydraulic places would not sell one anyway due to liability reasons. si I took the original, coated it with silicon and made new feather edges and have been using that jack for over 20 years now with no problems. Allways use jack stands though for safety.