The component with the lowest price in the CHAIN CASE schematic is the Screw 6x10.
Parts such as the Chain Case: Bolt(10x37), Nut, Case,chain Gz1, Washer (10.5x24x2.3) are included in the Gz250 Marauder 2003 (k3) Usa (e03) Chain Case parts fiche.
Check out any of the eight Chain Case components enlisted.