Looks like several of us are selling the GT sissy bar. I listed mine on Ebay, though I have it listed on the classified section here on R3 as well:
I bought the Triumph Rocket 3 GT Phantom Black and it has the silver version of the passenger backrest. I wanted the black version, so swapped it out. This has 80 miles exactly on it without any passenger so is essentially like new. Will ship well packed in OEM box my black backrest came in...
www.r3owners.net
@Triumph Rocket 3 , since you have the GT, I am assuming you’re asking about a taller backrest that could support a T-Bag style luggage. Corbin makes a backrest that is much taller than OEM and bolts directly onto the GT backrest bracket. Otherwise, you might need to blaze the path on a new product.