I went with the Givi tank bag that attaches to a ring you mount around the fuel filler cap. Works amazing, and have it tied into the 12V bike system so I can charge a few things at once. Also holds the phone in a nice see-thru window.
I love this bc I can use no bag, a small bag, or a really big one based on how long of a ride I’m going for. And super stable mounting since you can’t use magnet bags with the plastic tank fairings.
The Sena rechargeable phone mount looks pretty slick too, though I’ve never used it.
Where did you pull your power from and if it was the battery did you remove the tank to run the wire or what