Hi,
I guess the film coating we're talking about is just a transparent sticker to protect books cover.
Just simple as that.
You will find it at the stationery side of your regular store.
But be careful, some of these films are not perfectly smooth, and it will be impossible to apply uniformly. So not so easy to find.
Also, this technique is a little bit tricky, and take some time and efforts to achieve, so you will have to go slowly.
But if you succed, the result is rigid and protected enough.
Good luck !