I picked up 2 of these:
http://www.amazon.com/gp/product/B00...ilpage_o04_s00
Added both a 12v cig lighter and 2 USB.
1 is going under the bed for charging phones/tablets - and DW can use her 12v heating pad if we are boondocking...
The second is going outside for convenience...
To install near the dinette - take down the light (2 or 4 screws likely) and see how much clearance there is above it (before the real floor of the cabinet). What I bought needs a good 2 inches from the surface mount to clear the casing and connect the wires - others might be shallower.
Just a matter of snaking the wire from the fixture to the new hole - staying in that area should be relatively simple... I've tapped off of that area for new LED lights - and aux fans...