Replacement O-rings for selectable exhaust?

[PSDfreak]

I need to replace the orings that seal the solenoid rod into the exhaust pipe...They (2 small o-rings) go around the end of the shaft that turns that the flapper in the pipe. They are pretty small and I would imagine some sort of special high temp o -rings? Any ideas on where to locate these things??

The pipes are GIL marine pipes...The solenoids are Synchro Start solenoids.

Thanks,
Casey