Bob.
You will just have to join Facebook.
I know it has a reputation for people messaging about how many sugars in their tea and 'oh, now I am walking the dog LOL' etc. But, if you use it the way you want to, there are loads of good groups to join.
You don't have to participate (and you don't have to have thousands of friends).
You will find it easy to find those unavailable parts from anywhere in the world - not just eBay.
Lots of moped and microcar stuff - EACC, Moped77. Bubblecars micros & scoots etc.
Even Die-hard Nick Poll has joined.
Barry
https://www.facebook.com/groups/181148538580472/