The component with the lowest price in the AIR CLEANER schematic is the Tube,breather.
Parts such as the Air Cleaner: V.tube 11x15x420, Screw,pan,5mm, Duct L,air/c, Clip,hose 21.5 are included in the Gl1800a Goldwing 2001 (1) European Direct Sales Air Cleaner parts fiche.
Check out any of the twenty-three Air Cleaner components enlisted.