Parts such as the Repair Kit 1: O-ring, O-ring, Gasket, Cylinder Head 1 (nas), Oil Seal are included in the Xa800a-a 2002 Usa Repair Kit 1 parts fiche.
The component with the lowest price in the REPAIR KIT 1 schematic is the Gasket, Pump Case (nas).
On this parts fiche the Gasket, Cylinder (nas) is the most specified component.