Have you considered using a portable light powered from a 12 volt socket?
I can't find it at the moment, but I'll have a look at the equipment at work next week; there is a lamp that has an adjustable mount and an integrated switch.
Baja Designs makes a pretty cool little "dome light". Kinda expensive though.
https://www.bajadesigns.com/products/LED-Dome-Light-wSwitch.asp
You could also put a LED inside a rubber tractor lamp housing - and install a switch in the dead space on the back side of the rubber housing.
EDIT:
Found it. Betts is the manufacturer. They don't seem to have a website, or at least a good one. Google "Betts rotating work light" and you'll find it. Be careful, I don't think they all have the integrated switch.