Amazon has announced that those who pre-purchase the
Pokémon Sword and Pokémon Shield Double Pack, will receive a download code for an exclusive in-game Gold Studded Leather Case for their Pokémon Trainer. The offer expires November 14th, 2019 and the download codes will be emailed starting on November 15th, 2019.
Source:
https://www.amazon.com/Pokemon-Sword-Shield-Double-Pack-Nintendo/dp/B07ST7LY8F