The most reasonably priced component used on the Gb500 Touristtrophy 1989 (k) Usa California Swingarm is the Screw,tap.5x12.
On this parts fiche the Washer Fender Set is the most specified component.
A sample from the products for the Swingarm include: Collar.rr Fork (c, Chain Set, Drive, Slider,chain, Bolt.rear Fork Pi.