To obtain the Gang Green Safe Key needed to open the Gang Green Store Safe in Dead Island 2, travel to Venice Beach at the location shown before.
Once there, you’ll find Roach!
Take Roach out then loot the Gang Green Safe Key. Now that you have the key, travel to Gang Green (weed shop) nearby.
Loot the Gang Green Store Safe inside! You’ll then be able to pick up the Leeching Club!