I bought the Ninebot mount. It’s pretty good but I’m sure you could find something similar for cheaper. Don’t buy the older one that looks like this though, it’s terrible.

I would also be careful mounting your phone in general. The intense vibrations from riding can potentially cause damage to focus/OIS systems on newer phones. I only use the mount with a cheap Android phone for dashboard, I’ve tried putting my iPhone 13 Pro in it and recording a video and it was going crazy the whole ride.