On this parts fiche the Screw, Front & Rear is the most specified component.
The most reasonably priced component used on the Gsxr750 1990 (l) (e01 E02 E04 E15 16 17 18 21 22 24 25 34 39 53) Rear Fender (model L) is the Screw.
Check out any of the thirty-one Rear Fender (model L) components enlisted.