Rather than just getting a high resistance to drop the voltage I realized that a higher current would also. By putting a resistor in parallel with the potentiometer I can increase the current flowing through the first resistor and use a smaller, more available resistor there to drop the same voltage.

This is the schematic I did up in KTechLab to test my theory. the 1M resistor represents the smoke machine input. the max. voltage possible with this arrangement is about 30mV(50mV with a 5V supply). This means I should be able to supply the required 25mV for my max. temperature.