I installed a 6" dome light from Superbrightleds.com.
TDLS-NW36-G: Natural White - Gray Finish
125 lumens, not crazy but draws very little and lights up the whole cargo area.
Fits really nicely on the slanted part of the headliner. Attached it with two m4 16mm bolts. No cutting, just 3 small holes.
Thanks for the write up Snooper.