I use the one from gimbal-guard.com. I'm very happy with it for my P3 and P2 series Phantoms. The Trackimo snaps in there nice and tight, and yet you can remove it easily by pushing in slightly on the bottom front. The plastic will bend just enough for you to clear the tab at the top so that you can pull the Trackimo up and out with ease.
Trackimo sells a "drone kit" which might work okay but it's really just a bunch of velcro straps that you're supposed to attach to the leg. I like the gimbal-guard version. You can snap the Trackimo in and out in less than a second.
$17.50 with free shipping, but it takes two-three weeks from Israel (I'm in the US).