I used to have an RF900, and I was always disappointed in the overall lack of aftermarket goodies available for it.
Supposedly, Lockhart offered a carbon rear hugger for it, but it was on terminal backorder (typical of them!), and I finally gave up on it after about a year.
I've never seen a seat cowl for it. Maybe a Sargent upholstery job could do it, with the rear portion raised, for a simulated cowl look?
By the way, do you have an exhaust on yours? I've got a Micron carbon bolt-on can for it, about 95% new condition, and no scratches. I'd sell it to you for $100 if you're interested. If so, e-mail me...
Life is hard.
It's even harder when you're stupid.