Power cable to an AMPS mount

The Montana 700i only used with my snowmobile or ATV. The available AMPS mounts have power cable / data cable / audio cable, all this cables makes a big wire mess. The Micro-USB port does not feel water proof, and I do not like to use the Micro-USB port with the unit installed in an AMPS mount, it also looks like the screen is less bright when charging from the Micro-USB.

Does somebody have a wiring diagram for the AMPS connector pins, I would like ta make my own cable from a 12v-5v adapter to the AMPS with suited power cables lenght. Have hooked up Deutsch DT 2-pin connectors to my sleds and ATVs after the 12v-5v USB converter.