As I tend to be lazy and shop mail order....the only advice I can offer is that Ellisons do a portable day lamp (advertised as lightweight and compact!) Havent got it personally but if I were looking for a lamp for mobile work it would fit the bill!
Its in their current catlaogue page 289
give em a ring on 0845 130 6126
dunno what p and p or delivery will be like as I tend to wait till I need a bit of stuff before ordering to save on the p and p!
I guess that there are many more suppliers that would do a similar sort of thing so do ring aroound to check for the best deals!