2003 U320...from what I can see, the closest AC power gets to the dash is a pair of outlets to the left of the driver's feet. Is there AC power in the dash somewhere?
We have power strips on dash hidden in basket that is very useful for lots of things.
Source of power is the outlet on wall next to drivers chair, probably the same location as your outlet.
We routed a heavy duty extension cord though side dash panel, up under dash, then out on top of dash into basket.
Several years ago I installed a 400 watt inverter in the dash to power a nav computer .
Here is a writeup and pics
see Simple Pilot Bay inverter installation (http://www.foreforums.com/index.php?topic=29892.0)