If it's the seal onto the co2 bulb, I think it's similar to the baikal makarov. Just get some apprioate sized silicone tubing (fuel pipe) from a model shop or off that auction site and simply cut a new one from a short length of the tubing. Cut it slightly over length to allow a bit of compresionThen simply push into place around the piercer. You can make loads from a foot of tubing.