I wish I was one of the high school kids that spent the summer sorting and cataloging all those flyer parts. It is an amazing story. That is a great page you posted from their catalog, I didn't even know they had one.
I went through the parts list again today, looks like most of the plastic stuff is gone, other that doors, windows etc. I posted the link below, and not sure if there are other sites for their parts.
https://trainrepairparts.com/s...n-flyer-repair-parts
George