Thanks for the feedback, Bernie. I had found that information as well as quite a lot more details, but no source of said fasteners.
I have got a possible name that I have emailed, but have not had a reply to date.
I thought that, if Citroën were using these “standards” in the early parts of the 20th century, some of the RWD members might have run into (and hopefully solved) the problem.
Roger_G