Ok, so, basically, I won't pay for such a simple model - and neither should you.
So, after realising there is nothing readily available for free, and simple to print, I quickly designed my own.
Designed around an old Xiaomi Note 9 pro (165.8 mm × 76.7 mm × 8.8 mm), can be modified quite easily if you ask.
Exist with or without sunvisor, depending on your taste. (without looks funky, but it's wasn't the goal of the design).
Side opening for continous power / reloading.
Supposed to be printed without support, just be careful about part orientation.
No glue, magnet, patry trick, aviation tape or moon dust needed.
Print, mount in place with 2 M8 bolt in the base, slide the desired cover on top, and enjoy.
[edit:08/02/25]
Just edited the base file, as it didn't fit the phone - oopsie.
I made another version, a generic one, with the same dimensions, just a larger pocket for different camera placement. No idea which phone might fit, but worth the shot.
Also modified the M8 holes to make them adjustable in height.
Tried on the rig, it fits nicely, but my O shaped wheel prevents me from seeing it - so I didn't play with it yet, sadly.
The author marked this model as their own original creation.