I would suggest looking at the Marlin firmware. Various thermistors are listed.
Any thermistor could be used that is ok with the temperature (250C), fits in the hole and has a suitable resistance which means around 100k at room temperature but you would need to create your own lookup table for unlisted ones.
I ordered a few extra thermistors from the E3D manufacturer myself as a precautionary measure as the ones they supply are probably the easiest to fit.