Bought for mine about 18 months ago. Managed without it and got rid of the caravan about 6 months ago so doubt I'll need it now.
Few m of grey 7-core cable, back plate, socket, gaskets for the back of both sockets and split charge relay
On the forum £23 delivered or £20 to collect from near Beverely, East Yorkshire
Ebay link (ebay.co.uk)