These bikes have two accessory connectors which use a Sumitomo HM 090 connector. There is one under the driving seat, in the space beyond the fuse boxes, and another in the front fairings, usually on the left side that can be more tricky to reach.
On your bike they are both white two-pin connectors, where the (V)iolet with red tracer cable provides the (V)olts, and the (G)reen cable is (G)round. They also both share a 7.5A fuse (it may be 10A on new bikes, but it will be printed on the fuse box cover for OPT).
As a spare connector is used as cover to keep them waterproof, you only need to buy stoppers and pins to crimp your own cable.
For more details search for "Sumitomo" or "option connector" etc. on the site as there will be plenty of photos etc. from other people's projects.