Can I buy new Duster rear seat belts?

I don't take multiple passengers around in my car a lot, but do on occasion. With that in mind, does anyone make replacement retractors or seat belt sets for the rear seats in a Duster? Would like to get mine working again - the current ones are almost totally frozen up. If there's an easy way to repair them I'd be interested in that too, but with seatbelts I don't want some hack job that's going to fail when it matters.