There is the Colby MP-C895. 2GB with one AAA battery. It even has a radio.

Of course if you want to pack the Nano and a charger you can do that too. I have several pieces of the new Black & Decker VPX system. There is a USB charger charger in the system that works really well. I take it to charge my camera equipment when I am out hiking. I have never drained the battery all the way on a hike...I guess I need to test that.
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