I found these vintage new old stock computer cases on Facebook Marketplace. 4 of them are AT and the big one on the bottom left is ATX. They all come with the
Vintage Retro PC Case Beige Computer Case ATx at mid Power White Used full a3 | eBay
Old Computer Case Isolated On White Stock Photo 1046497807 | Shutterstock
Old White Pc Case 3D Model - .3ds - 123Free3DModels