Shiny Dialga, Palkia and Giratina Pokemon Black & White distribution events start in August, September - Neoseeker

All yours, so long as there's a local participating GameStop

Pokémon Omega Ruby / Alpha Sapphire FAQ/Walkthrough v1.71 - Neoseeker Walkthroughs

ALL MYSTERY GIFTS in Pokemon Black & White you can still get in 2021

Pokemon Black & White Official Game Guide, PDF, Pokémon

Event Discussion

Shiny Legendary Pokemon Dialga, Palkia, And Giratina - Pokemon Dialga Palkia Giratina Transparent PNG - 618x353 - Free Download on NicePNG

Pokémon X / Y FAQ/Walkthrough v3.01 - Neoseeker Walkthroughs

Eventdex - #0483 Dialga

2014springccmasscomm1061 [licensed for non-commercial use only] / Impact of the Pokémon Franchise

Pokémon X / Y FAQ/Walkthrough v3.01 - Neoseeker Walkthroughs

List of local English event Pokémon distributions (Generation V) - Bulbapedia, the community-driven Pokémon encyclopedia