I also use the charger that came with my Cassiopeia E-200. It's all but identical to the Axim AC adapter. Also, View MyPDA for a homemade adapter modified from a 4-port USB hub (powered) and link to Tips from the trenches in my sig for info on my homemade "scorpion" +5VDC regulator. Not for the timid. Note that I use the scorpion with a $10 car power adapter (set to 7.5VDC).
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E: here's an ebay search link, just as an example. Be sure your prospective adapter can support minimum +5.0VDC at 1.5A out if you want to charge while using your Ax. Should be 2.0 Amps if you have a big battery.
http://search.ebay.com/ac-adapter-pd...ageNameZRC0021