The Washer-plain-small,12 is the cheapest item from this partsfiche.
Parts such as the Swing Arm/shock Absorbers: Washer-spring,8mm, Nut,lock,12mm, Damper,shockabsorber, Nut,10mm are included in the Kd125 1975 Usa Canada Swing Arm/shock Absorbers parts fiche.
In this schematic the "Nut,8mm" is used most often.