From where please![]()
Try here http://www.uklight.co.uk/tethertools/usb-firewire-hdmi-cat6-cables.html
They have tether kits with good tether essential kits. With next day delivery
Maplin
Once you get to a long cable you really want an active extension. Just use the cable from your camera in an active extension from Maplin (or similar) and tape them together.
Alternatively, use a decent quality cable from somebody like Lindy but make sure it's no longer than 5 metres. Their transparent ones look pretty and seem to work well.
http://www.lindy.co.uk/cables-adapters-c1/usb-c449#t25