I've seen these on a few of Adidasguy's bikes:
(http://i1206.photobucket.com/albums/bb442/adidasguy/GS500/exhaust_protectors.jpg)
Where did you get these? Directly from the R&G website?
If I enter a GS 500 in their bike selector, it only lists protectors for aftermarket stuff (Scorpion and Yoshimura)...
Browse them by product rather than bike and you should find them.
I order direct.