This is my headphone holder, which prints all in one place, and does not require any supports. I have provided the AutoDesk Fusion archive file and the Inventor part file, so you can customize the mount to match your headphones and desk.

The parameters of the file are set up as follows:
deskThickness: thickness of the desk being mounted to, in mm

deskIntrusion: the amount that the mount wraps around the desk, specifically how deep it mounts inwards
deskIntrusionWidth: the width of the part that hangs onto the desk
headphoneWidth: the width of the supporting part for the headphones, this is 9 cm in the provided diagram
headphoneHeight: the height of the headphones, this is 1.5 cm in the provided diagram

clampWidth: the thickness of the clamp. thicker means a stronger part, but the default will most likely be fine

Some filets may need adjusting for some of the options if they are changed too much.