Here's an alternative to the cheap dx cable people use to plug there lights into the battery pack.
Scroll down the page to Ext cables with waterproof DIN [11mm DIA joint] connectors
1 meter version
http://www.rfconcepts.co.uk/camera_diy_kit.htm

Also available here from the same company trading under another name
http://www.cameras-cctv.com/diy-kits...eight_11mm-dia

5m upwards here
http://shop.reversingcamerasuk.com/e...26%20cables%22