This is a custom elytra, but this model is not official from the game. This wing was created by me, however, it was slightly based on a mod (Wings Mod link: https://www.curseforge.com/minecraft/mc-mods/wings/files), and on some custom elytra models on the internet. It's not so difficult and complicated to assemble, but it requires a little patience because of its size, which was calculated to be proportional to the size of an articulated character.