On this parts fiche the Bearing(20x27x23.5) is the most specified component.
The most reasonably priced component used on the Gsxr750 1989 (k) Usa (e03) Rear Cushion Lever (model L) is the Ring,stopper.
A sample from the products for the Rear Cushion Lever (model L) include: Spacer,rr Cushion Lever, Cushion,reservoir Tank, Lever Set,rear Cushion, Washer.