A lot of people are looking for items that wild pokemon can hold, like the Light Ball, berries, type-boosters like Black Belts, etc. But instead of catching a whole lot of that pokemon and checking if they're holding items, teach one of your pokemon Thief, which I believe is found behind the Galactic Eterna Building. Make sure the Thief-ing pokemon has no held item. I'm pretty sure most Dark types can learn it, but others like Luxray can, too. Anyways, walk/fly/bike/surf/whatever you do to get there to the area where the pokemon holding the item you want is found. Every time you encounter the wild pokemon, use Thief on it. EX:

Wild Chansey appeared!
Go, (insert the name of the pokemon who knows Thief here)!
What would you like to do? (Fight & select Thief)
_______ used Thief on the Wild Chansey!
_______ found an item!
(LATER) You take the item from your pokemon and it's a Lucky Egg/Lucky Punch.

NOTE: Exceptionally rare items like the Lucky Egg and Light Balls DO NOT usually appear on your first try...took me 6 Elekids to find the Electirizer! XD