Parts such as the Carburetor (component Parts): Screw-washer,5x16, Wire Stay, Screw, Gasket Set,a are included in the Cb500 1998 (w) Switzerland Carburetor (component Parts) parts fiche.
The Screw-washer 5x10 is the cheapest item from this partsfiche.
In this schematic the "Screw-washer,4x14" is used most often.