Looking for a reading progress bar plugin

Hi there

I’m looking for a plugin that would get me a nice reading progress bar like the one you can see on this website : http://www.slate.fr/story/93373/finlande-apple (or custom CSS code is that can be achieved without any plugin, but I doubt it).

I found various progress bar plugins in the WordPress plugin directory, but not for the readers : they all seem to be for a blogger who wants to display his own progress on some project.

What I’m looking for is something automatic, that fills itself up to 100% as the visitor scrolls down the page.

I guess something like that wouldn’t work with any theme. I’m using Hueman, and my website is here : http://reseaux-chaleur.cerema.fr

Thanks !