Perhaps the reason it is not common to find a "deer head target" is because most hunters do not commonly take head shots. If there was a big demand for that type of target someone would be making them.

Take a lemon and sit it on a pop can. If you can hit the lemon or the pop can every time at the distance you intend to shoot, then you could probably go for head shots at that distance.

But be aware that if a deer just turned its head at the moment you are squeezing the trigger the small target could move, say, an inch or two. That would not matter with a chest point of aim but for a head shot it could mean a miss or worse (a wounded deer). I think there is a time and place for a head shot but I have always managed to find a better option.

Robin