You can get the data from all Pokemon, items and other Mystery Gifts (Gen 1- 9) from the Event Gallery. Use PKHeX to import the data to your games.
https://projectpokemon.org/home/files/category/2-event-gallery/
If something isn't in the gallery, you could check if it's in the Github repo. If it's not in there, it probably doesn't exist or hasn't been contributed yet.
https://github.com/projectpokemon/EventsGallery/tree/master/Released