All sorts of homebrew adaptions have been made, and some have slightly modified off-the-shelf holders to work with the existing transmitter clip's ball joint.
The simplest one I saw was using the stock clip with a piece of pvc plastic or similar that had been shaped into an elongated "S" - put the bottom of the tablet onto the bottom jaw of the slip, hook one end of the plastic S over the top of the tablet, hook the bottom end into the top jaw of the stock clip. Simple, secure, instantly swappable if you want/need to use your phone for some reason.