euro hydraulics will be able to get you one in. But try Exchange Engineering 01476578505
get them to send you out a catalogue. good gear, good prices. but like i said, that place you got your hoses from will do you a lance no probs. ive been back there a few times, for hoses and alot of fittings.
EDIT: just re-read your post mate, so you wanna keep your gun and just change the lance? where your lance screws into your gun is normally 1/4'' but the gun end is usually female. but its always 1/4''