Here's how you can find hidden items in the games you mentioned:
* Pokémon Diamond, Pearl, and Platinum: Use the Dowsing Machine to find hidden items. You can get it from the Pokétch Company after beating the game.
* Pokémon Black and White: Use the Itemfinder held item. It increases the chances of encountering a hidden item when walking in the wild.
* Pokémon Black 2 and White 2: Use the Itemfinder held item.
* Pokémon X and Y: Use the Dowsing Machine app on your Pokédex. You can unlock it by completing the main story.
* Pokémon Omega Ruby and Alpha Sapphire: Use the Dowsing Machine app on your Pokédex. You can unlock it by completing the main story.
* Pokémon Sun and Moon: Use the Island Scan feature to find hidden items on islands. You can unlock it by completing the main story.
* Pokémon Ultra Sun and Ultra Moon: Use the Island Scan feature to find hidden items on islands. You can unlock it by completing the main story.
* Pokémon Let's Go, Pikachu and Let's Go, Eevee: You don't need any special items to find hidden items. You can find them by walking around and interacting with sparkling spots on the ground.
* Pokémon Sword and Shield: Use the Dowsing Machine app on your Rotom Phone. You can unlock it by completing the main story.
* Pokémon Brilliant Diamond and Shining Pearl: Use the Dowsing Machine to find hidden items. You can get it from the Pokétch Company after beating the game.
* Pokémon Legends: Arceus: You can use the Hisui Pokedex to discover new Pokemon. You can also use the Dowsing Machine to locate resources, but you will need to obtain it first. You can get it from the "Jubilife Village" after reaching "The Galaxy Team Headquarters."
Remember that the availability of hidden items and the tools to find them can vary depending on the game. It's always a good idea to check the game's manual or online resources for more specific information.