Imagine if there was an open source version of this.
You could use an open source laser cut or 3D printed stylus,
A tripod with an adjustable double camera mount like this one,
and open source OpenCV code for object tracking.
To keep things cheap, you might be able to get away with replacing the stylus with a wooden pencil, a ping-pong ball, or a custom tracking pattern you could print on paper and glue to your own custom stylus. Even a block of wood with a nail protruding would work as long as it was calibrated.