You can buy it on ebay, its called DIGITIZER FOR C5, approximately 10 dollars, the problem is they don't sell it with the black faceplate, which means you have to keep the old one, and trust me it's very hard to take it off the the touch screen without damaging it.
What you want to do is separate the old broken touch screen from the faceplate, the best way to do it is to warm it up with a hair dryer, I recommmand you to buy two of them just in case...