Snowdown Mystery Box where?

I read there was supposed to be a special Mystery Gift that increased the chances of getting a Snowdown skin, so I went to go check a couple of days ago, but there was no option there. So, I assumed that maybe I had to wait for the new Snowdown skins to release, so I did, and yet still I dont see the option in the store. :(

Is that part of what the 4AM maintenance is for?