Commissioned by Coffee Woozel, it's a really detailed custom plush.
This large, complex plushie was custom designed and made by TrashKitten, right down to the clothing and patterns. It's not for sale, but she would be willing to make a new and improved version as a commission.
SincereMasterpieces started making custom Krystal plushes last year and I think she will still do made-to-order Krystal plushes if you ask nicely.
Mancoin posted photos of Krystal cosplay and plushie.