The fifteen Zx550a1 Gpz550 1984 Europe Uk Fr Gr It Fg Sd St Footrests component parts are all listed in this schematic.
In this schematic the "Bolt-socket" is used most often.
The most reasonably priced component used on the Zx550a1 Gpz550 1984 Europe Uk Fr Gr It Fg Sd St Footrests is the Bolt-flanged,8x18.