Where do you buy kelp essence in Coral Island?

Excuse me, I'm wondering if you could assist me in locating kelp essence in Coral Island? I've been searching for it quite diligently, but it seems to be a rather elusive item. Could you possibly guide me to a reliable source where I might be able to purchase this elusive essence? Or perhaps, do you know of any specific shops or markets in Coral Island that specialize in selling such items? It would be greatly appreciated if you could share any insights or suggestions you may have.