appliance for maintaining correct water temperature?

How does one solve the problem of keeping a large volume of water at the correct temperature during the duration of multiple cleansing enemas? Are there appliances out there with 1 gallon or more capacity and a temperature contol that will go low enough? My searches have not come up with any. (All I have come up with is tea pots with low capacity and min temp settings of 140-deg, -way, way too hot. Ideal temp would probably be 40-deg-C or 104-deg-F.