You can get a full backrest and seat at Corbin, but it will cost you. I bought the rider, passenger and backrest from Corbin and it was damn expensive. Although, since I ride almost year round and commute to work on the Busa I could not be happier. The rider seat is finally now really starting to come into its own after about 1500 miles.
There are hundreds of posts on here about seats, you may be better off taking some time to research them and look over the pictures along with the posts.