All that's, in there is a connector block, a variable resistor, a switch and a linkage to the actual pedal.
I'm sure you could make one out of an old radiogram and some sheetmetal!
Cheers, Mick.
A radiogram??
I made one, you can see it here.Many of the older transformer TIGs have high-power rheostats; my Airco uses a 150 watt, 25 ohm one.