How do you find pokeball sellers in Pokemon game onyx blue?

In Pokémon Onyx Blue, you can find Poké Ball sellers primarily in Poké Marts, which are usually located in towns and cities throughout the game. Look for NPCs in these locations who sell items; they often have a Poké Ball icon above their heads. Additionally, some trainers may offer Poké Balls as rewards after battles or as part of side quests. Exploring the game world and interacting with characters will help you discover more sellers.