It appears this pet is temporarily unavailable on the Blizzard Store. Aradek on the Customer Service forum had this to say:
"Lil' XT has been temporarily removed from the store, everyone. We plan on bringing Lil' XT back as soon as possible, though. While I don't have an ETA to provide, I encourage you to check back over the course of the next couple weeks. :)"
514 pets
"Lil' XT has been temporarily removed from the store, everyone. We plan on bringing Lil' XT back as soon as possible, though. While I don't have an ETA to provide, I encourage you to check back over the course of the next couple weeks. :)"
Source: http://forums.worldofwarcraft.com/thread.html?topicId=26227282739
I assume this has something to do with fixing his voice...