...there's a charity used bike parts operation in Marin county here that does the same thing as Freewheel in Madison.
I mostly can't afford to buy stuff from their shop either. They sell used chain rings by the tooth count.

They have a derailleur I could have used on this 50's project, but I ended up buying one from England, because theirs was priced so high.
I can't figure out with the pandemic if this business model will continue to be successful, because of everyone stuck at home doing projects, or if they'll run out of volunteers to disassemble all the donated bikes.