I had some craft magnetic blocks lying around and designed a headphone stand around those.

This uses two craft magnet blocks approximately 22mm x 47.5mm x 10mm, I added a few tenths of a millimeter around the magnet to account for variability in the magnet's size. If it is too loose for you just add some hot glue, however, mine didn't need any.

Should fit most headphones regardless of size and weight, each magnet is rated for 3 lbs (approx 1.5kg).