There's two mounting points on the front of the handlebar covered by rubber plugs. They are threaded M8. You can use that to mount a 1" RAM style ball to and then mount whatever you want to that, or you can use it to mount the official Segway phone holder.
Here's a short video I made of the official mount: https://m.youtube.com/watch?v=JFbdc9Odkcc
And here's one I made showing the 1" ball system before I got the official mount: https://m.youtube.com/watch?v=oZCsCblGCM8
The handlebars also have M6 threaded holes in the ends of them that can be used to mount most bar-end mirrors made for metric bikes. This is what I have on mine:
Get you some mirrors:
https://www.amazon.com/dp/B07NYQ834N
And a phone holder:
https://www.amazon.com/dp/B0C1RY27RN
(Make sure you select the P-series version and not the universal one)