@jamiltron posted this a while ago on the OSR discord, I’m adding it here again so I don’t have to keep searching it up. Feel free to add below
Old School Fantasy Miniatures
Ral Partha
Northwind Miniatures
Oldschool Miniatures
Wargames Foundry
Warmonger Miniatures
Satyr Studios
Red Box Miniatures (whenever Trey decides to cast again)
Krakon Games
Armor Cast
Midlamm Miniatures
several of Reaper’s Dungeon Dwellers are old-school-ish (they have the rights to the old Dungeon Dwellers line, but reprint none)
Knightmare Miniatures
Mirilton
Diehard Miniatures
Dunkeldorf
Heresy Miniatures
Lead Adventures
Alternative Armies