The Washer, Plain (646) is the cheapest item from this partsfiche.
The forty-seven Ft9.9g 1988 Crankcase - Cylinder component parts are all listed in this schematic.
Parts such as the Crankcase - Cylinder: Cover, Thermostat, Screw, Panhead (a93), Bolt Hexagon (676), O-ring (168) are included in the Ft9.9g 1988 Crankcase - Cylinder parts fiche.