12v LED would be my suggestion. Then you would just need to take a spare car batt with you and power it that way. I have a load of 240v LED lights in my garage even the 10w ones are really good. And one of these makes a brill inspection light and no worry about dropping it and the bulb going pop.
You could look at this sort of thing ? http://http://www.amazon.co.uk/Rupse-OffRoad-Floodlight-Waterproof-Aluminum/dp/B00ASVZ0IS/ref=sr_1_7?ie=UTF8&qid=1375526298&sr=8-7&keywords=12v+led+work+light
What sort of use are you looking for with the light? I bought an advanced headlight from Halfords clearance at 3 and although it was the last turkey in the shop the aluminum cased 1W Cree led is amazingly bright and should last a considerable time on 3x800mAh Ni-MH AAA. It would make a good supplement/backup in any case as you'll need a fully charged car battery to last an equivalent time on a 24W.
12v solar panel, a big car battery and the above mentioned LED lights! we put a A3 size solar panel on the front of the garage to charge the batteries on the Audis thro the winter, worked a treat til someone damaged the panel with a football.
