The bike salvage is a good idea. I really hadn’t thought about that until you mentioned it. Thanks.
Might depend a bit on where you live, but there are a few rural bike shops around me that also have entire sheds and lots just filled with old bikes. You can generally find what you need and it costs a few bucks. I got an entire 70's schwinn frame for 20 dollars a few years back.Dumpster bikes used to keep my pedal bike rolling. There was no going an getting new tires, it was "hey, this bike in the garbage has good tires, looks like my bike gets new shoes!"
Or, as GW said, even just dumpster diving for bikes, or buying the super cheap/free bikes listed on marketplace here and there can be a good resource for some parts. Just depends on what you need.