4 gallon cans definitely got locally produced, and the plant for doing so in the field is mentionned in RASC training pamphlet no. 8.
British water jerry cans were of a specially embossed type with a different lining as of 1947 (when "The Jerrican, Notes on its care and use" was published). I think i've got a 1945 one somewhere. Theres a couple of threads on HMVF that may help (hope it's OK to link across) -
http://hmvf.co.uk/forumvb/showthread...ater-jerry-Can and the one linked from it.
That probably doesn't help with the 2gal cans though.