When you're sailing the Great Sea, you've probably seen Gorons in hats wearing backpacks, right? If you've talked to Zunari, he'll give you a Town Flower, asking you to trade with other merchants. I know there are Gorons on Bomb Island and Windfish Island. Go to Bomb Island and trade Town for Sea Flower. Then go to Windfish, and trade Sea for Exotic Flower. Go back to Windfall and get the item.