You could also just recalibrate the freezer thermostat so it will run above freezing, no controller needed.
If you look closely, inside that little hole is a calibration screw. For my freezer, I had to turn that little guy clockwise probably 4 turns. It takes several days to dial it in with this method, but the end result is no controller needed.
Adjust it in the morning, leave a container of water in there and let it sit for several hours. Check it in the evening, and adjust as needed. Repeat until you get the temperature you want.