Harry Potter could own custom-made wands or enchanted jewelry in fanfics. Also, some stories give him secret diaries or ancient magical tomes with hidden knowledge.
There's also a possibility that it's a Chinese Fireball. These dragons are very beautiful and powerful. In a fanfiction, the author might choose this type of dragon for Harry Potter to own because it would add an element of exoticism and grandeur to the story.
Well, it could be a magic item shop. Since Harry Potter is from the wizarding world, he might sell things like wands, potions, or magical artifacts in Konoha.
Perhaps it's an island with a hidden wizarding school, similar to Hogwarts but with its own distinct features. There might be ancient spells protecting the island, and the architecture could be a blend of different magical styles. Harry could have discovered this island during one of his adventures and decided to make it his own. He might use it as a sanctuary for those in need or as a place to study and preserve rare magic.
Well, perhaps it's a planet with its own system of magic. It might have a core made of pure magic essence which gives power to all the magic on the planet. And there could be different regions, like one area filled with floating islands where powerful wizards live.
It could be a magical sailing ship. Maybe it has enchanted sails that can catch the wind of magic and sail across different magical realms. Or it could be a small, personal ship that he uses to explore hidden corners of Hogwarts lake.
It could be a sleek, enchanted schooner. With sails that can change color according to the magical energy around it. The ship might have a figurehead that comes to life and gives advice, like a wise old wizard.
In the fanfiction, he might own a building that is actually a magical library. Since Harry has always been interested in knowledge, this building could be full of rare and ancient magic books. It could also be a place where wizards and witches from all over come to study and research, and Harry, as the owner, would be in charge of protecting these precious knowledge resources.
He might read ones that focus on his relationships with his friends, like more in - depth stories about his friendship with Ron and Hermione.
It could potentially be a black mamba. Although they are extremely venomous, in the wizarding world, Harry would have the magic to handle it safely. The black mamba is very fast and agile, which could symbolize Harry's own quick - thinking and agility in the face of danger.
Well, it could be in a story where the magical world has different rules allowing for such a situation. Maybe it's a alternate universe take.