We have a local-to-us family-owned hardware store, not affiliated with any chain. They've been around for about a hundred years and have a remarkable selection of even the most difficult to source bolts and other fasteners, all sorted and stowed away in drawer after drawer in aisles of antique wooden storage. Used to be that every town or section of the city had a place like this and we're fortunate to still have ours - there's a similar place in the next town over from here. Anyway, it's not unusual for me to visit them in search of some odd or end, and they nearly always have what I'm looking for, no matter how esoteric.
I don't buy in bulk - there's no need, they're a quarter mile away. They sell nuts and bolts one at a time, so if I need an M5 it sets me back seven cents. A matching washer? Another two or three cents. It actually keeps those stray pennies in my car sort of relevant. I have no idea how they stay in business with me buying things 23 cents at a time.