Last time I looked Custom airseals only had rams for steel trigger Gamos. They look like your photo the end of the ram has a free floating thick washer with an indentation to hold every thing central. So a washer say 1/8th thick with a drilled indent and you might be back to usable provided no other damage.
Anybody know where I can get a new piston
If I understood the discussion correctly, I think there was either an error during reassembly (easy to do with that trigger design) or the trigger was adjusted too far.You then removed the trigger+gas-spring+piston assembly from the rifle still "cocked". During some probing the trigger released and the gas spring fully "extended" outside of the rifle throwing parts around the room. Glad to hear you were very lucky to escape serious injury.That kind of gas spring event is usually fatal to the gas spring. Its "extension" must be speed & distance limited by the rifles internals (piston travel, air compression, & stop). When a gas spring is compressed and allowed to freely extend it will hit its own internal "stop" at full speed. That stop is NOT DESIGNED for that kind of impact and the gas spring will usually be damaged or destroyed.Probably what happened here... https://www.amazon.com/gp/customer-reviews/R3R0INIYHH7INBOther problems from the "release event" could be scratched or bent gas spring shaft which will cause premature seal failure, assuming it still works now.The "cap" at the end of the shaft that is missing/detached from the gas spring is really just a centering spacer. Important, but it may not need to be attached to the shaft. Once correctly assembled inside the rifle and proper preload compression is applied that centering spacer should be well confined and will go nowhere until the next time the rifle is disassembled.Still hoping I'm wrong, but I don't think those models of Gamo rifles can use Crosman NP1 or NP2 gas springs. Reasons & some measurements here...https://www.gatewaytoairguns.org/GTA/index.php?topic=200314.msg156337818#msg156337818Good parts links already supplied by Deeco :-)
piston and trigger were in my hand it and it went off sent the it all flying across the room into the wall .. so the new seal did its job lol but I did something wrong