Parts such as the Rear Fender: Washer,plain, 6mm, Bolt,hex 6x10, Fender Rear are included in the St50 Dax Germany Type 2 Rear Fender parts fiche.
In this schematic the "Bolt,hex 6x10" is used most often.
The component with the lowest price in the REAR FENDER schematic is the Washer,plain, 6mm.