Very cool looking bike. You can use just about any seat (Bonne, Thrux, Scram, etc.) from any year '01 and up. They'll all fit. I've had a modified Bonneville seat, a Thruxton Gel seat and a Corbin Gunfighter. The Corbin is the firmest of them, but it is also the most comfortable to me on longer rides. The Thruxton Gel seat is a very close second.
Fender Elimination Kits (FEK) are available from any number of our vendors. They'll incorporate a taillight, license plate mount and usually a plate of some sort to protect the underside of the seat/wiring. Installation is pretty straightforward. You can also find turnsignal brackets that will move the rear signals to the vicinity of the upper shock bolts, or you can fab up just about anything that suits your fancy. There are also LED taillights that have the turn signals integrated in. Again, pretty simple to install.
"Cognito Ergo Wrenchum"