If you really are out in the feeld, most time a car, truck or other work-machine is within reach.
There's the needet 12V / 24V handy.
But to be clear.
I only have a cheap soldering station and some constant temperature rain pipe soldering iron.
The few instances, I needet a soldering iron in the fielt, I used a blow torch which heated a pice of thick copper wire.
(Which worked better then expected)
But if I had to solder in the field more often, I wouldn't use one of this USB-soldering iron.
I would get one of thegood brand replacement-holder and cuse one of the manny kits (like the one Dave gor in one of his last mail bag videos) to connect it to a drill batterie-pack, car batterie, or wathever is within reach.