The item: "Roach Carapace Pauldron" I can't figure it out?

It's from the February 2019 Collection set. If no one is selling it, you'll need to wait until February next year and purchase the February 2019 Collection with CSC and open it choosing the Roach Carapace Pauldron as the item you wish it to have inside.

As rare as the February 2019 Collection where it came from, so only one for sale for 50 mil. It can be bought again from cash shop next February though.