Digital Cowboy will be putting out a supplementary lithium-ion battery for fifth-gen iPods at the end of the month. Call it a full tank of gas for the DAP world's version of an SUV.
Plugging into the dock connector, the DC-PC5GBT should give an iPod about 11 hours of continuous video play when used with the usual not-very-good Apple power unit. The 52 x 27 x 112mm battery weighs in at 116g and takes about 6 hours to juice up. It'll cost approximately $68.