Heating a hanging waterer

[sciemi]

We have an automatic hanging waterer in our coop, it has insulated/heated water line running to it but the water in the bowl freezes now. It can't sit on a heat plate type deal as then the stopper stops the water flow. Any ideas?
I have a disability and use a wheelchair so am unable to carry water to the coop.

 

[BWKatz]

Could u put one of those hot water heater covers on it?