given the very tiny size difference btwn the X1 and X2, I would imagine most cases would be interchangeable. Have you checked out X1 case thread? They Beyza slip cases are really nice and would definitely fit the X2, check the last page for mine.
Loving Sony hardware & the Android app store, BUT trying to patiently deal with transitioning from stable, "everything always works" Windows Phone to "always needing an XDA fix" Android.
SonyEricsson T68i / SonyEricsson T616 / HTC Tornado/ HTC Touch Cruise / HTC Touch Diamond 2 / Apple iPhone 3G / LG KS20 / SonyEricsson Xperia X1a/ LG Optimus 7 (e900h)/ Sony Xperia SL
HP Touchpad/ HTC Flyer/ MS Surface / Sony Vaio Duo i7