Adapted the clip part from another model, and added reinforcement to the bottom edge where it printed poorly. Added this angled raised section designed to take a phone mount adaptor where the bolt attachment is behind the centre of the screen. I have used a generic, widely available spring-loaded “phone mount adaptor for tripod” that takes a ¼" threaded mount directly behind the mount, but my Nothing CMF Phone has a button right where the mount would go - hence the offset and multiple hole options. 

Hole at the back is adequate for every USB-C cable I've tried so far so the controller can be charged without removing the clip.

Print with supports, I have confirmed this clip is flexible but strong enough with 5 walls and no infill.