Here are the two options I considered.
A: The DPS-9000+, made by digipower, is a rechargeable 7.2V battery, with connectors to almost any digital camera and every PDA, including a 5V voltage step-down connector; around 6000mah, I think. I haven\'t ever used or seen one of these, just pictures on the internet and some guy\'s website saying how he has one (search for zaurustuff in google and you\'ll find it.) On eBay, you can et one for $40-$45, but for ~6 extra hours of battery life, that\'s a pretty good deal.
B: Homemade external battery pack. Yeah, I suppose you could buy a $17 battery pack on the internet, but you can also buy a $2 battery holder at teh radioshack, get a fitting plug from an old unused AC adapter, or buy a plug from the previously mentioned radioshack for ]$1, solder it together, and you have youself a battery pack that will work fine for 1.2V batteries. For 1.5V batteries, connect an N4001 diode (also found at the shack) into your circuit.
The 1.2V NiMH batteries you will want to use in your pack are not too expensive. I got 4 2300mah batteries and a 3-hour charger new on eBay for $16 including shipping, and they work like a charm. You can add other features to your battery pack depending on how much money you\'re willing to spend, how much time you\'re willing to put into it, and how much experience you have with this sort of thing. It is possible to make a pack that uses 1.5V and 1.2V AAAs, AAs, 4/3A\'s, Cs, Ds, can switch polarity to charge the aforementioned 1.2V batteries from an AC adapter or a USB port, has many different cable extenders, velcroes to the back of your Zaurus, and has your girlfriend or boyfriend or husband or wife or favorite celebrity\'s face painted on the back. It\'s all up to you. I just made a 1.2V AA extender, and just recently I spent 2 hours on the way home from Six Flags watching Futurama from my CF card with the light on full and my extender did not even run out, not to mention the internal battery still being full. In addition to high-capacity NiMH AA\'s (don\'t use NiCads, they suck), you could also get some 4/3A size rechargeable batteries - they are only slightly larger than AAs and hold almost twice the charge. That path is further explored at
http://www.tekprosystems/zaurus/ , which has some other cool Zaurus mods, including blue paint and a keyboard light. However, please remember that 2300mah 1.2V x 4 = 2300mah 4.8V, not 9200mah 4.8V. It took me a while to realize that.
So, basically, you can get 6 hours for $45, or 2.3 hours for $19 (plus another 2.3 hours for every set of high-capacity NiMH AAs you buy)
I hope all this info helps, and I hope you haven\'t fallen asleep listening to my incessant ranting
