Electric+charcoal can be done too.
I do that in a converted GOSM type smoker.
You put the electric coil above a small bed of charcoal and wood chunks.
The coil starts the coals and gets the wood smoking, and then you adjust temp by switching power on and off to the coil. An ordinary oven thermostat could be used. Depending on the insulation value of the unit, a 120v element like one from the Brinkman electric might be sufficient, but gutting an old household oven might be fairly simple.
A heat sink made of some fire brick around the area of the heat source will improve recovery time for when the door is opened.
You can set a steam pan above this heat source to fill with hot water and catch drippings from the meat.