Warning: Spoiler! (Click to show)
you can order it at the ghpc (giant hidden placket club)
srsly I got mine off of ebay a while ago. No idea what season it is but it seems quite old. Id be interested to know. It is a giant, detachable , hidden placket. I guess u could experiment with different ways to button it maybe ?? i never tried.
Edit : btw, the way KG used it with the Attachment jacket totally kills. Awesome layering, they look like they were designed to be worn together, on that pic.