You should be able to purchase it, like any other main evolution stone, at a certain floor of the Celadon Department Store.
A thunderstone
You can buy it at the celadon pokemart mall.
I think you can only get it by using a thunderstone on an eevee. You get the eevee from Bill in Cerulean City.
Evolve Eevee by exposition of a Thunderstone.
On FireRed (and LeafGreen, Blue and Yellow) you can BUY thunderstones, firestones, leafstones and waterstones at the department store in Celadon city. It's really easy.
Yes, it's the only way to get a Raichu in any pokemon game
Raikou? I think you mean Raichu. To get a Raichu, just use a thunderstone on a Pikachu and it should evolve into Raichu. To get the thunderstone, go to the Celedon Department store or find one at the power plant.
Answer:Here's A Secret: thery're a secret(; You could use the itemfinder where you find zapdos and get a thunderstone. also you find mewtwo in cerulean cave.
You need surf, you'll find on at New Mauville (the route is under the cycle bridge to the east) There'll be a thunder stone in the complex. You can also collect Yellow Shards from using Dive in the Ocean and trade them for a Thunderstone. Otherwise you can simply trade with FireRed/LeafGreen with a Pokemon holding a Thunderstone.
Evolve the Eevee you get given at the top (using the back entrance) of the Pokemon 'Mansion' in Celadon using a Thunderstone.
The Pokémon that evolve via the Thunderstone are Pikachu which evolves into Raichu and Eevee which evolves into Jolteon.
With a water fire or thunderstone for sure. Possibly with freindship during the day or freindship during the night.