As the guys have mentioned, there are some other, cheaper, solutions but you can buy a mini-screen..If you want to shorten by cutting your own down, I'd be tempted to remove the screen screws and gaffa-tape it back on and lower it, incrementally, until you find your optimum height and then do the maths and cut accordingly.
http://www.adventuremoto.com.au/ya-f...60z-windscreen
and
http://www.powerbronze.de/9203025/75...-(315MM).model
..