The Meca System skid plates that Nick mentioned above sure look nice and very well made with nice stainless mounting hardware. All their stuff looked nice. No US importers. Get on it Go Fasters!
Here is a link to thier site which is mostly in French. Many of the Gas Gas pics didn't open for me but if you go the the DOCUMENTATIONS section you can open a PDF catalog of all their stuff through 07 and it has the GG stuff and pics also.
http://www.mecasystem.fr/
This is a KTM skidplate to give you an idea but the GG is similar
Skidad in MA