Just about one month ago I posted about the Life Jacket Returning and listed some new exclusive items. One of the items, the Stealth Tracker, has already been released. The Sumo Belt and Sumo Wig have not yet been out, however I am being led to believe they are now since the artwork for them now exists in Club Penguin’s files.
The Sumo is a head item.
The Sumo Belt is a body item.
Here it is on your penguin: (Thanks Safej16!)
Update: It is for the June 2012 Club Penguin Magazine. (Thanks Pengumile!)