After you battle and beat the gym
battle lass "Dana" to get her phone number, after waiting a while (2 gym's or just alot of walking and training) she will call you and give you a thunderstone after talking to her again (in front of her)
Route 28 and Mt. Silver
Route 47 is in the cave at Cianwood City
you go to route 9 and in the grass This is in soul silver only Heart gold players
After you battle and beat the gym
You can get a Thunderstone from Bill's grandpa, Lass Dana (she's on Route 38,) and the Pokeathalon Dome. You can also win it as a prize from the Bug Catching Contest.
battle lass "Dana" to get her phone number, after waiting a while (2 gym's or just alot of walking and training) she will call you and give you a thunderstone after talking to her again (in front of her)
Show Bill's grandfather the Pokemon he wants to see, get Lass Dana phone number, and she could find one, she is on Route 38, one of the stones that can be won in the Bug-Catching Contest by placing first, or winning the Pokéathlon Dome on Wednesday, Thursday, or Saturday.
Soul Silver: route 36 Heart Gold: trade with Soul Silver
No.
On route 44.
Route 28 and Mt. Silver
Yes you can but only in soul silver not in heart gold.
You can find it at Route 22, Route 26, Route 27, Route 28, Mt. Silver and Safari Zone
in Pokemon soul silver catch it in route 36, route 37, and route 48. (Note that i don't know if it is the same for silver)
Route 47 is in the cave at Cianwood City