If your area has a bike recycler, sometimes called a bike kitchen (which I dislike as a reference term), they might have some 20+ year old parts on their shelves. Our local non profit (R Community Bikes, mission is to get bikes into the hands of needy people) doesn't intend to sell just parts but if one befriends them (maybe volunteer, certainly donate) they have been known to help out some of us.

There's not really enough potential customers to pay for a retail based used bike shop in most communities. Craig's List, Facebook Marketplace are two more on line potentials. Andy