Enclosed Trailer

I'm looking at buying an enclosed trailer to haul my Demon in, don't want to go too large, extra cost, extra weight harder to maneuver in tight spots plus a storage issue. And surely don't want it too small in order to put some extras inside. So what's a good size for the car, small generator, small grill, fold up pop up umbrella an a couple of lawn chairs? I have a 16 ft open car hauler now that is barely long enough.