Geoff,
The 3d printer heater I think is a traditional coil heater embeded in ceramic in a metal case - sure some Googling will give you the answer...
But they are interesting - the one you have I would guess is 12v 40 watt ( so draws 3amps 'ish ).
You can get 60 watt and 100 watt (long body). ( Google - Dernord Cartridge Heater 12V 100W)
Here's the confusing bit - 3d printers have got temperature control and to do this they use - "a thermistor" - but not as you know it!!!!
The temperature control uses this type of thermistor sensor where different temp = different resistance which you can measure and therefore determine temperature.
A Controller senses the resistance and can control power to the heater to maintain desired temperature
Another suggestion for your melting pot - could you spray the fog fluid into the heat chamber rather than squirt?
C-3PO