RE: CEN GX1 GP
For parts try ehobbies or toyhaus both have some GX1 parts. You might have to contact CEN. They say they will continue to support discontinued models.
I believe the GX1 uses the NT16 motor, if it does a piston and sleeve can be gotten from ehobbies or toyhaus.
Sorry but I really don't know anything about the GX1.
rolland