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When I had to pass drug tests for probation as a kid I would get someone with clean urine to pee in one those metal hip flasks ( metal, not plastic, because it retains heat better) . I would put it inside of a cooler cup ( to help insulate) and put hand warmers ( those little packets you put in your gloves if your skiing and have cold hands) inside the cooler cup with the flask. I would duct tape it to my boxers, with the top of the flask where my zipper is. Having it up in your crotch helps keep it warm too, body heat. It worked once every two weeks for 8 months, and stayed warm like that for up to 4 hours. I've done it without the hand warmers and it's worked as well. Good luck.
Crisis precipitates change.