Help Needed: Ganged Rheostat

Colvern Ltd are the company to supply this - the internet will give you a list of suppliers.

I have rebuilt a dual-ganged pot with junk box pots. I used the original shaft and wiper portion of the pot and replaced the resistor element with one of the same diameter. Thankfully, both sections weren't bad. If you don't have a junk box, there are several surplus electronics companies (findable on the internet) which sell assortments of potentiometers as well as individual ones. By the way, a lot of times, pots are not chosen by wattage but rather by value. I suspect in your case the 100:1 ratio for fine and coarse adjustment is the reason one section is 400 and the other is 40K -- it just so happened that it's rated at 2W. I would bet the 400 ohm portion is used as a potentiometer, and the 40K ohm pot is wired as a rheostat (two terminal, variable resistor) in series with one end of the 400 ohm section which sets the voltage to a control portion of the power supply, rather than controlling anywhere close to 2W of power.