I'd strongly suggest that you get the towing guides from the manufacturer(s) you are interested in and use that as your guide to what you need. That way you know exactly what the manufacturer ,states the rig can handle. There MAY be an SRW out there that works.
You also need to make sure that you really do have a 3600 lb pin weight. We full time, and ours is supposedly around there, but the way we are loaded, my actually pin weight is 4200 lbs, thought we are still under the 19,500 gross for the trailer. We full time in our TH so YMMV.