The pins for the handlebar hinges on early bikes seem impossible to find - I have tried UK and Germany. I found an alternative here - the pin that connects the gearstick on a Citroen 2CV! They are cheap but plus postage from Germany.

Scroll down on this page - stitch it together, I am not allowed to post urls or images yet
franzose.de/ en/Citroen-2CV/ ACDY/Gangschaltung-Gestaenge/