This is where the nice maker folks can help out.
Its not hard to make an accurate non contact thermometer and IR chips from old defunct security scanners can be used.
The method I found is to use a drone or phone vibrate motor, take off the weight by crushing and solder a pair of wires to the connector.
Simple beam interrupt is all you need here and a single high gain bipolar transistor such as 2SD965 as the preamplifier.
Connect output of the preamp to a very basic readout such as a battery meter, run motor at about 1V and there you have it!
Add lens to fit, using the good old fashioned cylindrical casing from dead till roll method.
Calibration isn't too hard if you happen to have a kettle (100C) and ice (0C) along with a piece of flat black plastic as the
reference or pyrolytic graphite if you wanted to go all high tech.
I have a modifed calibrated IRT here which now has a yellow LED backlight instead of the red dot as needed it for other projects.