GSS is a Chinese company that makes LCD protector screens for cameras. I purchased mine from Amazon for $12.74, which is a very reasonable price. NOTE: this is an optical glass protector, i.e. NOT a plastic sticker cover (like ones for your phone), but a hard glass-like cover that has some thickness.
According to the company’s website, the protector screen has 6 layers, and it has non-explosive properties, which means when the screen breaks, it shatters into little pieces (like a car windshield), instead of large chunks of sharp objects. This would protect your original LCD in case the protector screen breaks.
The one I purchased included a protector for both the live-view LCD screen and the top small LCD screen. Putting the screen on was pretty straightforward (although for some reason the instructions were only in Chinese). One thing you must note is that this screen will replace your “Canon” logo on your LCD with GSS logo. So if you are for some reason a “Canon” logo lover, then this probably isn’t good for you.
I think the screen creates a little bit of extra glare (as you can see in the picture bellow) but I really don’t consider that an issue, and doesn’t really affect my working with the camera.
Overall, I don’t think you can really go wrong with most screen protectors, and I am content with my purchase.
Before and After Photos: