The most reasonably priced component used on the Z50je Monkey Finland Crankcase - Oil Pump is the Screw,cross 5x10.
On this parts fiche the Bolt,flange,6x65 is the most specified component.
Some items from this specific schematic: Shaft,pump Drive, Clamper,over Flow, Bolt,flange,6x60, Tube, Fuel5.0x350.