I mean, half of my hammers have had their handles remade with whatever hardwood was closest. So I'm gonna go with those.

However, the most complex thing that I can repair with sourced parts would be either my truck, or my truck. I've had to fix it with "close enough" parts before, and I will fix it until the frame rusts (which given Northern states and salted roads probably won't be more than a few more years)

There's a smattering of electronics that I've seen mentioned multiple times as well.

One thing that is theoretically repairable, but is hard to find parts for, my washing machine. It's a old 50s model with a lever to engage the motor, a roller on top to squeeze water out, and a simple steel gear system to drive everything. I should be able to open it up with a crescent wrench and flat head screwdriver, but I doubt I will ever be able to find ready-made parts (I have looked briefly when I thought I had a problem with it that sorted itself) but I might be able to bodge some things together if needed.