Brad,
There are a few people in Aust that can also help,
the guy who advertises in the back of VMX mag does good seat restorations, also has a mould of GP2 tanks (not sure what your after), rods are best changed to the Yamaha YB125 unit (some crank work is required)
My experience with the U.S. guys are that they are unbelievable expensive.
Phil Young is also a ossa guru, Firko would be able to let you know if he's still around.
I will also P.M. you some details of a guy down the Goldie who is a bit of a ossa tragic...he may help, he may not. I sold him a gp2 a few years back,seemed like a nice guy.