How do you get the copycats doll in Pokemon SoulSilver?

You can't get a Copycat doll in Pokemon SoulSilver.

The Copycat doll is a special item from the Pokemon games *Diamond, Pearl, and Platinum* that can be used to evolve Mime Jr. into Mr. Mime.

Unfortunately, this item and the ability to evolve Mime Jr. in this way are not present in Pokemon SoulSilver.