check this out...

You could buy some car batteries and possibly take an old power backup unit and use that interface with the car batteries, then hook this bad boy up with a FW800 out to your laptop and you'd be set. Just power the thing up and down with use...

Might wanna consider some wheels for carrying it around :P
"Fix it 'til it Breaks."

Jacob - EiC & Director of Technology
Mac Pro Quad 2.66 - 4GB RAM
160 GB SATA RAID 1 - 650 GB Storage
Quad 19" Widescreen LCDs
Accessorized to the Hilt