Update 11/2011 - Dolgin Camera Power solution
Take a look at these products - 10-15 hours of run time and low cost. They ship worldwide:
I was able to build a custom battery for the GH2 using the Panasonic dmw-dcc8 DC adapter and a hobby RC car battery. Watch for more information.
One thing I forgot to mention is that the tip of the Panasonic DC coupler is positive so you need to connect the red wire from the battery to the white painted wire of the 6 foot cable.