Parts such as the Transmission: Needle Brg, B/brg N/rad N/com, Gear,low, O Ring,24.5mm are included in the Cb250b4 Germany Transmission parts fiche.
In this schematic the "Set-ring, 25m/m" is used most often.
The most reasonably priced component used on the Cb250b4 Germany Transmission is the Bolt,hex 6x8.