I think some hair pieces (like the "wigs" from the hairdresser) had their own partnumbers.. Have no idea if they're available though.
Ages ago there was a "hair add on", but long gone. A real shame.
As far as I know, most hair is part of the klicky these days, and not available as a separate order... If you find out otherwise, I'm interested too - need one of those ridiculous new hairs from the officers in the pirate theme