Guild Wars 2

So, I fell in love with the Marauder’s set in sPvP, and I decided to craft it for WvW and PvE.
I went to the Master Crafters, bought the recipes for the inscriptions and insignias, then went to town. I made a full set of armor, weapons and trinkets, pardon one rather annoying to find piece.

The back armor. Where the hell do I get this? It shouldn’t be any more difficult than the other pieces, so A-Net, what’s up? Where’s it hiding?

To note: I found this back piece I can likely put the Ebony Jewelry upgrade into,
http://db.dulfy.net/item/69598
however there is no place to locate it.

To put a level 80 jewel in a stat-selectable backpiece you need spinal blades. All the other stat-selectable backpieces are either level 78 (crafted), or ascended.