A DC powered soldering iron would work from a car or ebike battery (with a dc-dc step-down converter if using ebike battery). A TS100 for example works great. I use mine from RC car LiPo batteries.
Gas (propane) irons also exist, although I'm not sure there's many that are aimed at electronics. There'sUSB powered ones too, and even ones that run off usb-c with higher voltage, which you could use from a power bank (TS80 for example).