Movie Summary
Only a few people are aware of this that I know of. This secret was going to become public sooner or later.
This took me approximately 100+ hours plus the assistance of 2 high level priests.
Create a new character. You must virtually complete all Ratchet, Booty Bay, Gadgetzan, Gnomeregan, and Everlook quests. All quests must be of red difficulty to your character.
Completing the quests will generate a large amount of spill over reputation with the Gnome faction.
Once done, you will be able to purchase a Gnome mount from a very specific vendor. I'll leave it up to you to find them.
Note: This technique only works on Gnome mounts. I am unaware if another Horde race can purchase the mount or not by following the same steps.
.