This is the Handler. It is a floating handgrip for GoPro cameras, If you play in the water it is a great little product. It's $29.99. So I found myself at the beach in need of one of these. But there was no place to pick one up. Then I noticed that the cap to a 20 ounce coke bottle was about the same size as the old non-quick release tripod mount. I found a screw in my car that was the right size - 3/8ths inch I believe is standard tripod size, total dumb luck - and combined these parts.
The only part that was tricky was making a hole in the bottle cap with my knife. There was a good chance that I would cut myself, fortunately it didn't occur.
It floats incredible well. In fact if you let go of it in the water, the whole thing inverts with the bottle sticking straight out of the water, and the camera below - a great way to shoot underwater I suppose. If you want it less buoyant, just add some water to the bottle. Even with the bottle full of water it floats. Total cost? $8 for the tripod adapter, $1.79 for the coke, and pennies for the screw.