Standard industrial slotted trunking, available from any place that sells DIN mounted relays, PLC, and other industrial logic. Even from electrical wholesalers. Available in quite a few sizes as well, though you will typically have to buy a length of 2m or so of each size. You probably want the largest 100mm by 100mm for mains wiring though, the smaller ones work well for 1mm solid core cable inside a machine.