seventeen components are shown in this Xl500s 1981 (b) Usa Handlebar / Top Bridge 1 - Chart exploded diagram.
On this parts fiche the Bolt,flange,8x36 is the most specified component.
The most reasonably priced component used on the Xl500s 1981 (b) Usa Handlebar / Top Bridge 1 - Chart is the Bolt,flange 8x65.