If you want touch on your laptop and you're not ready to upgrade yet, you should check out the AirBar. You do need to buy the right bar for your screen size though. It's obviously not as good as a real touch screen, but it seems like a decent substitute until you can get one.
Product Site: http://www.air.bar/
Video Review: https://www.youtube.com/watch?v=QR5r1EfvheI