The connectors are AMP ones, have a look on the RS website http://rswww.com you need a trade account to order them, but your local marine electronics dealer will be able to get them for you, or PM me.
Radio Spares will almost certainly be able to supply one. They are on the web. Call into a local Maplins if you have one. It looks like a fairly standard 4 pin connector but make sure you know the diameter of the central plug and the number and position of the little alignment keys. AW Marine at Haslar will also be able to help you. As you say there are about 5 million different types/sizes of connector.