Trophy 1200 Phone Mount Options

The top yoke nut is a good place. Drill and tap the nut and fit a Ram ball.
If you’re not confident doing it yourself, this guy makes the mounts. http://www.telferizer.com/products/

 

Hi I've loosened my left handlebar and placed fairly large washers under the left hand two bolt fittings. The bolt closest to the key gets a flat bar ( same thickness as the washers) with a one inch ball on it . Replace the handlebar and position the ball towards the right hand side of the bike. Tighten the tree allen key bolts. Now bend the ball to the middle of the handle bar behind the key position and upwards. Now you can fit any phone carrier that you like onto the ball. I've used the one shown in the attached picture. I've also picked up power from underneath the cubby hole to the Phone holder. There is a usb port underneath my holder which I use to charge the phone while riding.

 

Wonder what your final decision was. The mirror mounts on the Street Twin are both right hand thread M10 x 1.25. I think a fairly standard thread for mirrors, but some have a left hand thread one side.