Pelipper, Chansey, and Happiny.
By using Thief/Covet/Switcheroo/Trick or Pickpocket/Magician, you can find wild Pelipper (very common) or wild Happiny/Chansey (5% chance) with a Lucky Egg. Also, probably easier, just catch them.
Hope I helped!
Lucky Egg Serebii
This video should show you how to get a lucky egg.