The most reasonably priced component used on the Cbx1000 Supersport 1979 (z) England Oil Filter - Oil Pump is the Washer,plug,drain 12.
Parts such as the Oil Filter - Oil Pump: Bolt,flange,6x35, O Ring,, Drain Cock, Dowel,pin,8x14 are included in the Cbx1000 Supersport 1979 (z) England Oil Filter - Oil Pump parts fiche.
On this parts fiche the Bolt,flange 6x25 is the most specified component.