WoWDB

Edit:  Digmaster's Earthblade had its functionality removed when the associated season of Brawler's Guild ended.  As far as I know, it's still possible to acquire the item, but it will not do anything.

The fastest way to farm for this item is to farm Pandaren, Mogu, and Mantid archaeology digsites - then crate the artifact solves and exchange them for  Crate of Tol'vir Archaeology Fragments.  This method does require that you have 600 skill level in the profession, and is certainly much more efficient if you are able to fly in Pandaria.

It took me - on my mage, so I could travel faster than most - about eight hours of using this method before I looted Digmaster's Earthblade.