This was inspired by Jeremy's great Koss Porta Pro Headphone Holder. https://www.thingiverse.com/thing:3615447
For those, like me, with either a strangely shaped head or ears where they shouldn't be, this does the same job but uses the far cheaper Koss KSC75 Clip On Headphones and gives far more adjustability by using a ball and socket joint mounted on the headset. The phones can also be held just off the ears, if you prefer, rather than pressing on them which I find more comfortable.
As Jeremy suggested in his original text these will flip outward, like on the original Rift CV1, to allow for easier headset donning/removal.
At the time of writing the headphones can be obtained for under £19 at Amazon UK or under $15 at Amazon USA rather than the Porta Pro which is about £33/$34.
You will see, from the photos that the original ear clip is retained but cut off where the metallic part leaves the plastic housing. This is to enable the clip to the pushed snugly into the 3d printed holder. A decent pair of pilers will accomplish the cut quite easily. You can discard the silicon part that is meant to go over your ear.
You can also remove the original cable clip on the left side of the Rift to allow more room for the new clamp, I've incorporated a new cable guide to support the DP/USB cable on the headset. I also use velcro cable ties to support the cable towards the rear of the headset, this allows the cable to drop down my back instead of getting in my way on the left side. This is not a necessity but I find it useful.
The headphone cable that comes with the Koss is, of course too long. I've just bundled it up and attached it to the Rift DP/USB cable with another velcro cable tie but it would be a lot tidier if you could shorten it. My soldering is not that good so I'm leaving well alone.