I would experiment with the chemical or rechargeable pocket warmers. If you could find or repurpose some sort of harness to have them placed where you want the heat applied that might work. Perhaps consider using them in conjunction with a gel pack to provide greater coverage and heat distribution. I use the "Hot Hands" brand chemical type and they last from 8-10 hours and are fairly inexpensive. I think some gel packs can be microwaved also, so that may provide some relief in your hotel.