I have found the perfect Pokemon for the job. Grab a [Noivern][1] with the ability Frisk (one of its natural ability, and easy to spot), teach him Thief, and then go fishing for wild Luvdiscs. If one is holding an item of interest, just thief. If not, then KO it or run away. Remember to take the item from Noivern before repeating! 


  [1]: http://www.serebii.net/pokedex-xy/715.shtml