I'd be very wary of pumping an extra volt into a sensitive electronic device such as a zaurus at the risk of frying something.
Without one of these units in hand I can't tell yiu how to get the voltage down to 5v even though it is repeatedly reference on the page you linked to.
Can you contact the manufacturer?
If indeed can't be done, I would say you have 2 options. 1, return it as it does not perform as specified. 2, add a resistor inline that will shave off that extra volt.
*disclaimer: I'm not an electronics guru, but I think it would work... do your own research and attempt at your own risk
Have you tried sticking a volt meter on it to see what it's actually putting out?
else, it seems like a nice power supply.
I occassionally use a BattPak (with iSun) from ICP Global and put a CLA in the provided port to drop the voltage down. Otherwise I schlep along the power supply and hijack power where and when I can (outlets are everywhere if you look for 'em)