On this parts fiche the Spacer(10x16x38.8) is the most specified component.
The Pin 20x20 is the lowest priced item on this Stand - Rear Brake schematic.
Parts such as the Stand - Rear Brake: Lock Washer, Washer, Nut, Bolt are included in the Gs450ez 1980 (t) Usa (e03) Stand - Rear Brake parts fiche.