Does such a thing exist, or can one be DIYd out of an old camera without too much cash outlay?
“Budget” and true thermal cameras don’t go together. Search flir.
At least not what most hobbyists consider budget. People have tried to use a single point IR temperature sensor to (very slowly) scan an area and build a image. There is also a camera on indiegogo but its still vaporware at the moment.
It might be cheaper to hire one? I’ve wanted one ever since seeing them used in The Apparition. 
if im right, they all over 1500$ 
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