I've been on the hunt for any 45mm burrs with two screw holes, but most of them are 55 mm and up. I don't know of any sites that list burrs by diameter, but if you know of one, that would be helpful.
A friend and I stumbled across an antique Kitchenaid A9 coffee grinder. It's in working order, just needs some cleaning up and replacement burrs, as they are pretty worn. I am having the hardest time trying to find some replacements that are in new-ish condition. I have attached a few photos...