You mean that there is no 12V output in the boot space? Hadn't realised this before. My current Scenic has one in the rear seat area, and the Galaxy has 2 in the cargo area.
Safest way is to run 12V lead to luggage area, then buy an inverter. I have one that plugs into the 12V socket. You can now get them shaped like drinks cans so that they can be fitted into cup holders