I'm not sure whether you mean the USB interface cable for programming the controller or the actual battery cable itself.
Two usb interface cables are available on the
GM Website, one for the internal controller and one for the external ones.
I expect many of the
GM dealers will also stock these cables, but you would need to check with your local dealer to make sure.
GM batteries are usually supplied with a battery lead, which has the correct plug to suit the battery outlet socket.
Alan