Onesie and K-pop can no longer be found in the game files of Fortnite.
The two skins were expected to release shortly after appearing in the data-mined game files, however that does not seem to be the case anymore.
K-pop first appeared in September of 2018 as a mysterious unnamed skin. A later update added the name “K-pop.”
It has remained in the game files ever since, until recently.
Onesie did not have the mysterious start of the K-pop skin, it showed up fully named and apparently complete in the game files near the start of Season 6.
The skin features a female character wearing Durr Burger pajamas.
Fortnite has released seasonal skins in the Item shop with Halloween approaching, including the Arachnid set and an Oktoberfest line.
It is unlikely that Epic would scrap completed skins entirely, especially ones that were as popular as K-pop and Onesie.
They may have been removed for reworking or bug fixing and could re-appear in a future update.