Be carefull! Hade the same problem with my sisters phone. I first tried to replace the Digitizer Glas, but its full glued on the LCD screen when I tried to seperate both the LCD broke. You have to replace the whole display unit. I bought them from ebay. Didn't find it on ebay.com but on the german site. It's about 90€
http://www.ebay.de/itm/Original-HTC-Desire-X-Display-Touchscreen-LCD-Rahmen-Glas-Digitizer-scchwarz-/151109377548?pt=DE_Handy_Organizer_Ersatzteile_Werkzeuge&hash=item232ed21e0c
Even this is the whole TOP-Unit it was still not very easy.
Hope I could help!