I really liked the headphone holder by Stevetecx because it's small, simple, and looks nice. My only problem was that it was structurally weaker than it needed to be. I reduced the overall length so it's now sized to hold heaphones with a maximum headband of 4cm. I also fattened out the bottom, keeping a taper, to help transfer weight from the tip of the holder to the base.
I also changed the orientation of the model so it prints the strongest possible structure.
Stevetecx says to use a 3,5x16 Screw. I just found a screw that I had left over from another project that ended up being a bit bigger. It caused a small split, but the holder is still strong enough now that I don't have to worry if my cat steps on it.