That's a standard electrical box. Any supply house will have a selection in various sizes. I've seen some of the smaller ones at Home Despot as well.
Although that's really not the best choice for an electronics enclosure. Machine tools generally use an oil-tight box to keep the crud out. Probably not a problem for your shop, but still something to consider.
As others have mentioned, try Digikey or Mouser for electronics enclosures. Or even eBay. The main problem with any of these suppliers is going to be the shipping to Alaska.