On this parts fiche the Nut,flange,6mm is the most specified component.
The most reasonably priced component used on the Gl1100d 1982 (c) F-19 Seat is the Nut,flange,6mm.
A sample from the products for the F-19 Seat include: Stay,r.seat Rr., Bolt,socket 8x12, Spg.seat Adjust., Stay,l.seat Rr..