I obtained them when I picked a rattle can-sprayed Batavus Hunter. They were in a small jar and handed to me with the notion 'This is broken'.
Even though the Batavus frame has rear U-brake mounts, it was not the frame it was originally meant to go on, I presume.
No more information than that...
Hi and welcome :)
What accessories are you looking for?
You'll mostly find trustworthy sellers on here: you can look for those marked 'Gold Traders', those are members that have dealt (bought/sold) a lot with good feedback.