There is a very good Ironmongers near here, remember those. If you want a single washer, they will sell you one. Or twelve springs and fork handles and hose, or whatever, and surprise, surprise, they are no more expensive than Mr B or Mr Q, (a twenty minute drive away) and they know what they are talking about.
I imagine I would need to wait until we have one of the frame sections to check the diameter of said bolt.