Hi there. The gigabeat F is generally an unpopular player, so there aren't many accessories for it, anywhere in the world.
My F20 has its screen protected by a thin film designed for a Palm, which I had to cut in order to fit it in. The iPod video's screen is slightly larger than the gigabeat F's, so you will need to trim it a bit for it to work. Generally, any screen protector will do, it's just a matter it making it fit. Cheap solution, does the job well.