Both the gem and the eye can be bought from the valor vendors in Townlong once you finish the quest lines from Wrathion
There’s currently no way to obtain an additional Eye of the Black Prince, and we’re aware it can create a situation where people are deterred from wanting to upgrade their items. That’s not the intent, we want you to use it and enjoy the upgrade then and there, and so we’re looking into a way for players to obtain additional sockets similar to how you can purchase additional legendary gems.
Unfortunately just the first gem sets you back 10000 gold. Granted a legendary item is well worth that much money but really... if you plan on upgrading 10k for the gem plus however the heck much for everything else is still gonna keep me from actually socketing anything.
Feb 13, 2013 -1
"YOU CAN REPLACE THE EYE OF BLACK PRINCE". Just fly down to Commander Oxheart. He sell's them for $2,500g.