You can take a car cord adapter and gut it. Get them for less than $10 on ebay. I already had one so it's what I did.

Open it up and remove the fuse goodies. Solder wires directly to the circuit board and put it back in the plastic. Seal it with silicone.

Put it under the fork shields behind the headlight. Just tie wrap it to the fork.

Wire it directly to the battery or pick up 12 vdc from the headlight circuit.

Or you can buy a hardwire adapter already made. Garmin Nuvi and Tom Tom use the same unit. They are $15 to $30 depending on where you buy them.

By wiring it to the headlight low beam circuit you will make sure it turns off when you turn the ride off.

 

I just tapped into the wire that runs to the front fender light.