The factory Harley one. Several types of pads available, depending on the seat you have (lots available on EBay), and the luggage rack is removable. I bought two sissybars, one luggage rack, and three pads, depending on the seat config I'm using. The luggage rack that comes standard is strong enough that I put the mount for my Givi 45L trunk on it and it holds no problem.
Could check out J&P Cycles, Drag Specialities, Bikers Choice, or any of the other catalog outfits, they all have a decent selection of parts and goodies to pick from.