Where do you get the ice stone on soul silver?

You can't get an Ice Stone in SoulSilver. The Ice Stone was introduced in Generation IV games (Diamond, Pearl, and Platinum), so it is not available in SoulSilver (Generation IV).

There is no way to obtain an Ice Stone in SoulSilver, making it impossible to evolve any Pokémon that need it, like Glaceon or Glalie.