Interesting links. The first is for American factories only, which is neat, but I'd be surprised if this case was made in America. I'm familiar with the second link, but I don't believe it's related to factories/mass production. The third link is being squatted on.
Ah yes sorry, meant fabhub.io. Ironic to get the address wrong as its my site. Belated disclaimer.
For outsourcing, alibaba.com and mfg.com are the big ones. Starting onshore / digital may be good for short run & prototyping. Trade mags and manufacturer associations have local directories.