I think the best solution is a RAM X-Grip to hold the phone, with a ball that screws right into one of the unused mirror mounts on the Ninja's handlebars. I have mine set up that way, but I'm away from my bike right now so I can't show a picture of it. The X-Grips now come with an extra rubber thing that really secures your phone in it. Ask me how I know this is a good idea.
Here is the ball that fits the existing screw mount in the handlebars (the holes have plugs in them that you have to pop out).