A PTC thermistor would be nice.
Just in case you didn't see it, we do have a new NTC Thermistor model in the "Thermal and Electro-Thermal" category of the SystemVision Component Library. It uses the simplified form of the Steinhart-Hart equation (with the single parameter "Beta"), because that seems to be the only data that is readily available from manufacturers' datasheets. Good suggestion from Johnny B. on needing a PTC version, I'll try to get that model added to our Library soon. As Norm suggested, will need to investigate what data is typically available from the manufactures for PTC devices.