The most reasonably priced component used on the Xl185s 1990 (l) General Export / Kph Seat is the Screw,tapping,5x8.
On this parts fiche the Bolt,flange 6x10 is the most specified component.
A sample from the products for the Seat include: Washer,plain,8mm, Nut,flange,6mm, Screw,tapping,5x8, Rubber,a.seat.set.