What do you call this, where do you find it?

I need to buy the kind of thermostat used to turn on a car's radiator
fan (or at least an electric swtich that will close at 120^ F or
higher) , and I also need it to use as a sensor a thin tube (2-4 mm)
that will go into a radiator or heater hose, between the metal housing
and the hose that surrounds it. Am I being clear?

I don't know what words to use to search for specifically this on
ebay/amazon/google. Do you know what words capture the "tube" part,
and in order to look at non-car parts, the turn-on/close-switch when
hot part?

Nor do I know what kind of car used/uses this kind of thermostat. If
I had a car make and model and year, I could find one that way. Do
you know a car that used such a thermostat.

Originally, I bought one from JCWhitney based on the picture in the
catalog, but I sold the car and forgot to remove the thermostat. ;-(

Thanks.