Reusable hand warmers?

I went down a rabbit-hole a few months ago, trying to find a replacement for single-use, disposable hand warmer packets. I want to bring a couple for my gloves since they have a small pocket on the back to store matching shells. The shells usually only come out when I need more warmth, but they only do so much.

I found a bunch of electric and reusable gel type hand warmers. It looked like the electric ones were too large, but could be used as battery backups for the phone. And if the gel pouches are anything like the cold-packs I've got perpetually in the freezer, I worry that they won't hold much heat.

Does anyone have a recommendation for a small hand-warmer that could replace the chemical pouches?

when you first asked the question my thought pattern followed you down the same rabbit holes it sounded like you chose. I think the gel packs might be worthwhile to try out. Unlike cooling your beverage or your knee, your fingers are giving off heat. Usually your not actually heating your fingers with these your just trying to take the chill off. Once they are warmed up it is easier for your body heat to keep them warm.

The gel packs look like they may be the best option, for now. I've read that they don't last long, but I guess I can bring a couple of sets and recharge by boiling if needed. It might be an okay system since I'd get a hot drink out of the process. Gel-pack tea, anyone?

We purchased 2 of the electric hand warmers on Amazon, they are about the size of a pack of cigarettes, they also double as a accessory battery pack, 10,000 mhr. Under $20. They have 3 settings, we use the low, med and high are way too hot. I rotate jacket pockets, when my hands start to get cold I just stick my hand in my pocket for a few minutes. If my core start to chill I put it in my shirt pocket and zip my jacket all the way. This thing really throws some heat. Put it in my sleeping bag and get nice and toasty. Too much heat to leave on all night. Runtime over 8hrs. on low! Recharges overnight. The only drawback......weight. A great trade off to stay warm.