John,
if you can find a flash that works off a PC socket, rather than a hot shoe, you could rig a large flash to run off a slave device that plugs in to the flash its self.
Its a shame you are in a rush, i have all the gear you would need. Both a big flash and this slave device.
They are not expensive..
see here
http://www.profilmgear.com/Items/12494?sck...0Shoe%20Adapter
Like i said, if you can wait abit i can send this and a big flash to borrow.
Matt