WoWDB

This is obtained by Tol'vir archaeology in Uldum. If you're lucky enough to discover the research project for this, I tip my hat to you! It is quite rare and you'll earn a fair bit of envy from mount hunters everywhere.

In other news, you can farm Pandaria archaeology sites and turn in the completed artifacts for Tol'vir fragments as an alternate way of getting this. I find this way to be preferable, as it takes a measure of luck to simply get Uldum digsites to pop up for you.

Good luck if you attempt to farm this mount! You'll likely be in for a long ride.