I installed a hanger for my seat belts but not the headsets (my jacks are at the corners of the instrument panel above the vents so hanging them with the belts would be problematic). I don't have any pics of mine but here's one that NovaBandit (Ed Kranz) posted. I have the same hanger mounted roughly in the same position and I think it works pretty good there. Unfortunately I don't remember who I bought it from.
Note that the 'wide' design holds enough of the belt so that buckles and adjustment hardware is kept out of bang your head range. How do the 'thinner' designs work in that respect?