This animation shows how the spot welder components are packed into the case:

I used a 3D printed panel (white part, STL files are included in Files section) and a generic plastic case (150mm x 110mm x 70mm model 'Kradex Z3W'). The modules are held with M2.5 or M3 bolts and nuts, and M5 bolts were used to mount welding cables on SCR module.

Depending on your region you may need to use a case from different manufacturer and make some adjustment to the STL files. You can also make a case of your own, or even use the spot welder without a case.