I like this idea, but when I try it, the ribbon easily slides up inside the notebook and the pen comes loose. I had an idea to improve this that would solve that issue; put some sort of stopper (maybe a button) near the end of the ribbon, so that when the ribbon rests inside the notebook, the stopper sits just outside the bottom of the notebook. This way, when the notebook is closed, the stopper wouldn't allow the ribbon to slide up inside the notebook at all. This way the pen/pencil on top would stay tightly in place (also with the assistance of the elastic band) until the notebook is opened.

Going to try to remember to try this once I'm home from the office and maybe make an Instructable on it too.

Thanks for idea and great post!