I have an enclosed 5x8 V nose trailer with ramp door that works fine for all my bikes including the ST 1300 . I can tow it with my Honda Element as it is just under the 1500 lb tow limit with the ST aboard so you should have no problem towing with your RV.
It has a ramp door and is fitted with a Condor drive in wheel chock . Drive in chock is probably a must have if you are loading the ST by yourself. The ST fits under the torsion bar for the ramp with windshield down but you have to duck if you are in the saddle powering in. I bought new approximately 5 years ago- IIRC the trailer itself was in the $ 1800. range but by the time I added the chock, tie down rings , spare tire and tube hitch/ draw bar and ball for the tow vehicle the numbers climbed into the $3200. area.
You will also need jacks at the rear or jack stands if you want to load or unload with the trailer unhitched.