I'm uncertain if Sena will make Ultraslim cases for the X, but I've found something similar. It'll protect against scratches but it's thin enough to not add bulk. It's not ultrasuede (synthetic) and not leather (which is a plus for me). It's got a good bit less design than the Sena, but it's also 1/3 of the price at just $10 (plus $2 shipping). There's also a version with a pocket on it so you can ditch your wallet and keep your cards with your phone.
Waterfield Suede Case
Waterfield Suede Case