Essentially you have only one viable option: BATTERY FLASH or MAINS FLASH w/ petrol generator
Broncolor make the Verso A4, a 2400w pack that can work via mains or battery. Take 2x batteries, and if you are concerned about freezing action, take either:
1x Verso A4
1x Bi-Tube Head
2-batteries (1x = backup)
or
2x Verso A2
1x Bi-Tube Head
(3-4x batteries)
and
1x pocket wizard kit.
The modifier looks like a beauty dish: either a silver or white interior dish: the silver is essentially a big hard dish, the white is more flattering, soft but directional.