According to Hellfire Taco's answer to this question, these shiny Pokémon can be found in Cherish Balls.
Entei, Suicune, Raikou, Eevee, Vaporeon, Jolteon, Flareon, Leafeon, Glaceon, Umbreon, Espeon, Sylveon, Pichu, Pikachu, Raichu, Milotic, Genesect, Magikarp, Gyarados, Giratina, Palkia, Dialga, Metagross, Larvitar, Pupitar, Tyranitar, Volcarona, Rayquaza, Golurk, Hydreigon, Gengar, Diancie, Tyranitar, Beldum, Metang, Yveltal, Xerneas, Mewtwo, Jirachi, Arceus, Charizard, Tapu Koko
(I bolded the Pokemon's names, in an attempt to make them slightly easier to read)
Seperate from this list, there is:
- Shiny Zeraora (Pokemon HOME)
- Shiny Solgaleo (Japan Only
- Shiny Lunala (Japan Only)
- Necrozma (Japan Only)
- Shiny Tapus (Japan Only)
- Mimikuyu (Japan Only)
- Poiple (Japan Only)
- Kyogre (Japan Only)
- Groudon (Japan Only)
- Gardevoir (Japan Only)
- Ho-oh (Japan Only)
- Volcarona (Korean Regions Only)
So, all of these Pokémon can be found as Shiny via their event distribution. Most have some sort of "Legendary" status (Literally and Figuratively), with them being iconic to the franchise in some way. For example, there is the Pikachu line, the entire Eevee line, Magikarp, and actual Legendary Pokémon.
I Hope I Helped!
In addition, I'll list HT's other source as well.