This does the jobs very well and you have a few spares if the first one doesn't go on perfectly. I suggest making sure the screen is as clean and grease-free as possible before applying and take your time.
Having trawled through the options, I opted for this one as it looked fairly neat and simple to use. So far it's not disappointed. It can bend to the angle you want and you can fold it away to put in your laptop bag. It gives off enough light to see the keyboard - plus you can use it to keep the screen brightness up when watching a DVD.