The Headlight assembly is constructed from several parts from which the Lens Asy is the most expensive.
Parts such as the Headlight: Screw, Pan Head, Rim, Headlight, Washer, Plate (517), Nut, Adjust are included in the Cv80 1986 Riva Headlight parts fiche.
In this schematic the "Screw, Rim Adjuster" is used most often.