I know you did not ask for opinions here but I would be remiss if I did not at least try to get you to reconsider your decission to pull a trailer with your motorcycle. Given the rather unforgiving laws of physics, it just does not bode well for a long and healthy life. I don't want to see anybody get hurt. The difference between a catastrophe and an accident is that one is likely avoidable with a little thought beforehand. I know, you can find Harleys and Goldwings all over the highway, pulling trailors. That does not change the fact that it is dangerous behavior. I don't know of any bike manufacturer that makes a trailer hitch either. Wish I could be more supportive on this one, but I feel you would be an accident looking for a place to happen. Life is short enough without looking for trouble. Appologies for being a wet blanket.
You sound like you've never towed a trailer. You claim towing to be dangerous behavior and yet, with a little research for statistics ... Well I can't find any statistical accident information on motorcycles pulling trailers ... So I think your claim is unfounded out side the fact that riding a motorcycle is inherently dangerous behavior. So no bike manufacturer makes a hitch ... There are a lot of after market things that they don't make for their bikes. That don't mean the stuff is detrimental to the motorcycles. I believe most who pull a trailer are very aware of what they are doing and take appropriate precautions. Like leaving greater distance when following. Traveling a little slower. Also from behind, most cagers give the trailer notice because they're visible from a distance. I pull and live in my camper traveling the open road 4 to 5 months a year and have never had a problem. Like most, when I pull, I use a little common sense. I speak from having over 30,000 miles of trailer pulling experience and enjoyment.