Where do you get a thunder stone in Pokemon Silver?

The only way to get the stones, (fire, thunder, leaf, water,) is by beating the Elite four, and then going to Kanto reigon. You can't get the stones in Jhoto. Sorry.

That is false.

Dana on the route 39 (i think)

if you registor her # she gives you rare stones

That's not correct,

The house where Bill is in Blue/Red is now where Bill's dad is,

He asks about pokémon, show him the pokémon and you get the typestone. Once you defete the elite four go to the pokeathlon place and you can buy them there for athlete points.Go to route 34 in johto and battle the picknicker Gina and register her and she might give you some rare stones. actually they're both right