Here's how:
1. Catch a Shiny Pokemon: This is the most difficult part. Shiny Pokemon are incredibly rare and you'll need to have some serious luck to find one.
2. Trade with the Game Corner Owner: Once you have a Shiny Pokemon, head to the Game Corner in Goldenrod City and talk to the owner. He'll trade you the Silver Feather for your Shiny Pokemon.
Important Notes:
* The Game Corner owner will only trade for Shiny Pokemon that are legitimate. This means they can't be hacked or cloned.
* The Silver Feather is a very useful item that allows you to revive a fainted Pokemon without using a revive or Max Revive.
* This trade can only be done once.
Finding a Shiny Pokemon is a difficult task, but with a bit of persistence and a lot of luck, you can get the Silver Feather for your Pokemon Soul Silver journey. Good luck!