They might be a seasonal item, but they are less than $20.

At the store you will find a small 200W "personal" space heater, made for "spot" heating. Like if you work in a cubical, it would keep you warm.

For a survival or emergency situation these could be very useful, maybe if you have a off grid solar system with a inverter and batteries, 200W isn't too much and could keep a small well insulated room warm. If pointed directly at you it could keep you from running a bigger heater.

Bundling up is probably better, but hands get cold when doing work so it might come in handy.

Being a resistive element, it would run nicely on the cheaper modified sine wave inverters, or even a old style square wave inverter.