Try BOC gases. They had them in a leaflet the other day on the counter. They were about $40.
These are thermostats used to control coolrooms. They go from -5 to 25 degrees. You can also change the temp differential.
To adjust you need a philips head screwdriver.
Ive been running one of these for 1 year in my fridge. Just connect the 2 wired from the original thermostat and this one takes over