I bought a few of these for myself, the woman, family/friends and they work pretty good. Looks like the "iHateTheCold" large hand warmers are on sale. FREE shipping on them, they have a powerful built in flashlight, and triples as a power bank.

$39 for the 8800mAh version, which is the same price as their smaller 4400mAh version:

Silver: https://www.amazon.ca/dp/B01BM6RH10
Pink: https://www.amazon.ca/dp/B01BM6N1Y2

Pretty good deal in my opinion, some power banks are that price without any other functions.