Where do you get the coin case in Pokemon emerald?

Answer 1

Go to the house next to the casino. When the lady says," I wish i had harbor mail" , go to the slateport Pokemart, buy harbor mail, go back and talk to her, and yes when she wants to trade you a harbor mail for a coin case.

Answer 2

Oh honey, you must be new to the game. You get the coin case in Mauville City, right next to the Game Corner. Just talk to the dude standing outside, and he'll hand it over like it's no big deal. Now go win big at the slots, or whatever you crazy kids do these days.