My sister was trying to grow plants in that thing. I told her she was an idiot and took it for cloning LOL. It comes with a sponge, but that leaves me having to cut the sponge after the clones root.. not optimal obviously. Cut up some rockwool cubes, cut clones put 'em in the clones then just let the water run. Nothing fancy and the water temperature is controlled by the room temperature.
You could probably rig something out of a computer fan controller if the pad runs on 12v. You gotta find a fan controller that comes with a thermal probe then attach probe and the wires to your heat pad. Not 100% sure if that would work, but I don't see why not. Something like
this should work, but I don't see how they don't sell heat matts with controllers.