With this model you don't bother replacing the thermistor as such, you just fit a new one.
As Service Agents for Waeco for many years, we did this regularly.
You simply need a relatively cheap replacement thermistor, they have replacement parts, and just some heat transfer paste, a small holesaw and a steady hand. You drill a 25mm hole around 40mm in and 25mm down from the underside of the dairy compartment, from memory. You don't drill all the way in, just enough to remove the plastic housing and then pick out the insulation.
Gets you a cheap fridge if you can do it and not destroy the evaporator.