On this parts fiche the Bolt,flange,6x28 is the most specified component.
Parts such as the Oil Filter - Oil Pan: Seat Relief Valve, Washer Seal, 6mm, Gasket,oil Pan (mca), Case,oil Filter are included in the Cb1100rbii France England Germany Netherland General Export Oil Filter - Oil Pan parts fiche.
The Washer Seal, 6mm is the cheapest item from this partsfiche.