Remixed https://www.thingiverse.com/thing:2728660 and attached a camera mount to it (e.g. GoPro).
Update Version 4:
The mount now comes in two parts. Two M5 nuts and bolts are now needed. This way the camera mount can be rotated. The notch for the zip ties are better positioned. The arm length is shortened.
Download the two V4 files for it.
Here is a timelapse made with this mount: https://youtu.be/BNgYbTcAZsQ
Update 2018-06-10: File MK3_camera_mount_v4-MK3_mount.stl was corrupt.
Update 2018-06-16: added a 2 cm longer arm for v4.