I would try to find one at the hardware store that works. If that doesnt work, Boss Paintball products carries the MINI Player parts kit. The Kit says that it comes with:
2 Bottom Section (Air Transfer Tube) O-rings
4 Top Section (Air Transfer Tube) O-rings
It should be one of those you need.
Titanium Karnivor Pump
: CCM Premium Pump Kit w/ AT, CCM 86* frame with reverse drop and on/off, CCM Internals, CCM Fittings, CP shorty Reg, CP detent
: Black #9927 / Kila Detents / Virtue Eyes
paintball is more than just a game...its a hobby