Where to get thunderbolt in Pokemon FireRed?

If you go to the game corner in Celadon city,you can buy alot of coins, ( which cost ALOT of money ) then go outside the little house next door, talk to the third(or second) person in the room, then one of the TM's are thunderbolt. also, on one of the people you can get a Porygon.

P.S, i think the amount of coins you need to get the TM is 4500.