When I go down route I take my normal line engineer toolbox, that has pretty much everything I need including a hacksaw, files, my own multimeter, gas soldering iron, etc.
With hand tools I think you can be pretty generous with what an engineer would have, especially for a story, also if the aircraft is a charter operation they carry a fair bit of spares. The 777's I work on have a fairly big spares pack up onboard. Don't forget the big aircraft also carry a whole load of cargo, not just passenger bags. You could have anything in there.
Re generators; without wanting to dig out my training notes, am I not correct in thinking that if a motor is driven, it becomes a generator? First class and business class seats are full of electrical motors, could one of these be jury rigged into being a generator? As I said, my little gas soldering kit goes with me on flights!
For some sort of steam shenanigans, the main engines and APU also have air starters, little air turbine motors. One of these connected to a generator on one end and a spanking big kettle on the other might give you a working rotating thing of some sorts!