Check out any of the sixteen Left Handle Switch (model Z) components enlisted.
In this schematic the "Screw" is used most often.
Parts such as the Left Handle Switch (model Z): Lever Assembly, Clamp(l:120), Lever,clutch, Switch Assembly,handle,left are included in the Gs450tx 1982 (z) Usa (e03) Left Handle Switch (model Z) parts fiche.