A bit OT but lacking any other options there is another alternative:

We have had good results warming people by assembling what amounts to a one person heated environment. One way is to get the person out of the majority of their wet clothing. Getting them into a poncho, with a liner if available. They sit on a sleeping pad cross legged or with knees pulled up with the poncho forming a tent around them. A candle, small oil lamp or carbide headlamp is placed between their legs so the knees, and hands if needed, keeps the poncho away from the flame.

The result is that the small flame rapidly warms the enclosed area and this warms the person even if they aren't producing much heat. In a few minutes the interior of the one-man environment is pushing 80F and warming proceeds rapidly.

I have used a similar method in wet caves. We would carry large garbage bags that formed the enclosure once a hole is cut for the head. When the symptoms of hypothermia became apparent we would all get into our bags and use our carbide headlamps for heat.