Parts ? You might try http://www.myronsmopeds.com/category/parts/wards-riverside-parts/
Or some of the other moped shops . They probably wouldn't have specific listings , so you should write them about whatever you're looking for .
If you're good at fabricating , that could go a long way .
One of the best things about old machines is you can make something that works and you'll likely be the only one that knows any difference . ;)