As I said, the most common contact temp sensors are either based on thermocouples (and for -100 C type T is a good one) or on PT100 (platinum resistance sensor) which is very accurate.
Most of the sensors at www.minco.com
are based on these two types, packaged as ready-to-use sensors configuration (note : RTD , Resistance Temperature Detectors, is actually PT100).
There are hundreds of companies that sell packaged sensor tips, insertion rods, washers and all kind of configurations, but the sensor itself inside the package, and this will lead you to the choice of electronics, is most probably either thermocouple or PT100.
If you just want to buy a packaged sensor, you may also want to try www.omega.com
- I used them in the past and they have quite a variety. They also have good engineering docs on their site.