If you are talking about the rubber that goes between the pressure plate and clutch seen below... you can replace the blue rubber piece with a faucet rubber gasket/plug illustrated in the lower photo.
Anyway, let me know if you're interested in buying the Strobe slipper. I can sell it to you. Heck, I will even sell you the complete tranny if you're interested. It has UE idler gears inside and locked in second gear. PM me.
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)