I carried one on my bike across Algeria for GPS and lamp batteries. It is possible to buy one from normal electronics shops (Maplin, Radio Shack etc) with a 12v car cigarette lighter adapter these days. (I fitted a pair of sockets to my bike) Mine was 20 UK pounds, and does NiMH and NiCd cells gave me no problems.
If you are an electronics fan, all you need for Ni-Cd cells is a constant current source to suit the cells you are using - easy!
I bought a charger, because it was the easiest way to get one already in a nice case, with the correct mountings for the cells, and an automatic cutoff when fully charged.
For interest, put part no L78AA into the search box on http://www.maplin.co.uk/