Things You'll Need
Instructions
Go to Ecruteak City in the Johto Region. Walk west until you reach Route 38. A girl calls you on your cell phone and tells you she found a Thunderstone. She transfers the item to your inventory.
Walk north from Goldenrod City to reach Johto's National Park. Enter the Bug Catching Contest on Tuesday, Thursday or Saturday. Catch the most bug Pokemon to earn first place. Your prize is one of nine rare stones, including a Thunderstone.
Walk west from National Park to find the Pokeathlon arena. Use your Pokemon to compete in events and win points. Talk to the lady at the prize counter on Wednesday or Saturday to exchange 2,500 points for a Thunderstone.
Walk northeast from Cerulean City in the Kanto region. Enter the house on Route 25 and speak to Bill's grandfather. If you have a Pichu in your party, he gives you a Thunderstone.
Transfer any Pokemon to the Pokewalker device via Nintendo Wi-Fi. Select the Yellow Forest route. Take over 6,000 steps while carrying the Pokewalker. The device keeps track of your steps, so you do not need to count them. Select "Dowsing." Poke the grass patches on the screen, and you may find a Thunderstone.