I've got a 23 amp PSU, used to run a couple of chargers and various things off it trackside.
Size is 18 (w) x 19 (l) x 6 (h), weight is 1.5kg, so iirc the same weight as your car with its gear in there.
Pics:
http://dl.dropbox.com/u/20670693/01092011306.jpg
http://dl.dropbox.com/u/20670693/01092011307.jpg
http://dl.dropbox.com/u/20670693/01092011308.jpg
£20 posted (inc £6.50 recorded 1st class post).