RE: stripped Head
If it's the NX26, then I am afraid that the head button can't be replaced as the heatsink is still a one piece unit on that engine.
The TR28, TR28 (SH Version), NX76, GST 7.7 engines all have a removeable head button. But the NX26, NX15, and NX18 (16 as well) these engines do not.