I use a waterbath for my small 25L batches as I can't put the probe into the Plastic fermenters . . . Well I can I just don't want to. :lol: Then a small aquarium heater in the water batch does a good job of keeping the temperature where I want it . . . I do drop a stainless cooling coil in them during the summer though. One of the small 30L under bed storage boxes would make an ideal water batch as it doesn't need to be too deep. Ideal for demijohns. . . . . You may find a small submersible aquarium pump (power head type) useful for keeping the water bath at a constant temperature throughout the entire bath.
I would not use any form of direct heating that was not controlled by a thermostat though . . . even if the instructions do say that you don't need one as the heating is very gentle :twisted:
