Install DC power cable connector on vacuum feedthrough rod
Depending on the model, the conductor rod thickness corresponds to common thread diameters (e.g. 1/4, 3/8, 3/4). You could thread the ends with a die which can be bought at an autoparts store or hardware store. They also can be easily had from an industrial supplier like Grainger, MSC or McMaster Carr. If you thread the rod, a simple set screw lug can be bought from a hardware store which is used for connecting thick electric wires to terminals. Just use two nuts, washers and a lock washer to secure it to the threaded rod.

For the smaller diameter conductor rods, solder a lead and put a plug on the end. Don't solder the thicker rods.