Cheap end bathroom lightweight 4 berth?

We currently have a 1992 ABI Celebration 450CT 5 berth. It is mid bathroom, double dinette payout which has served us very well and is in very good condition - no damp. I am interested in whether there are any lightweight four berth caravans with end bathroom configuration that is lighter than the MPTLM of 1300kg. I've been trying to work out whether its possible for me to pretty much swap our van for a four berth end bathroom one which can still be pulled with our existing towcar. Can anyone advise me of any vans out there? Many thanks in anticipation:)