hyperion, my seat is a Kawasaki OEM Gel seat, that I bought used from a former 900 owner. He already had the Utopia backrest installed on it, so I can't tell you where he got it or how much it cost.
What I can say is that I will never have another bike that doesn't have a driver's backrest on it. Makes all the difference when you can actually lean back into something. There is a thumbscrew adjustment which controls how far forward it leans. And there is one nut/bolt through the hinge that you can remove to remove the backrest, when you have something softer to lean against. It seems very sturdy to me, and I highly recommend it, especially in conjunction with an upgrade to the seat.