Where do you get a water stone in heartgold before you defeat the pokemon league?

In Pokémon HeartGold, you can find a Water Stone before defeating the Pokémon League by exploring the Ruins of Alph. Inside the ruins, you can obtain a Water Stone by breaking the rocks in the area, or you can also receive one from a hidden item location in the Ilex Forest. Make sure to use the Dowsing Machine to help locate hidden items.