Exotic back item with valkyrie stats?
Wiki is your friend: http://wiki.guildwars2.com/wiki/Back_items
From my short search, this does not exist. Closest is Cavaliers Backpack at Temple of Balth in Straits.
You can Forge Tempered Spinal Blades and select Valk stats.
We go out in the world and take our chances
Fate is just the weight of circumstances
That’s the way that lady luck dances
Fate is just the weight of circumstances
That’s the way that lady luck dances