Hacked into device. Supplied external power for the converter circuit. Problem solved.
For anyone interested, this is what you do:
The two halves can be pried apart without damage to the plastic.
The power is an orange wire. The ground is obvious... two wires coming from the cable shielding connected to the opposite side of the board.
Clip the orange wire to disconnect power from the XOOM (you don't want to backfeed and harm your tablet).
Connect the orange wire to your new positive voltage (5V, by the way). Connect the ground of you new supply to the ground of the board.
I used a portable USB power supply. Grabbed an unused USB cable and cut off the end. There are only four wires and a shield. The red is power, the black is ground. If the colors are different, buzz out the lines (Look up the connector specs on the web).
Then I drilled a hole next to the existing cable, being careful not to damage the locking tabs of the case. Used a drill bit the same diameter as the USB cable. Put some heat shrink tubing on the cable as a strain relief. Snapped the halves back closed.
It looks like it was made that way. ;-)
Works great.