2 thoughts come to mind. If you currently like the Harley you own all the trike companies you mentioned make a conversion for Harleys.
Thought #2 look at a Can Am Spyder. They are purpose built trikes,they are comfortable, they have lots of room(I am 6'2" 260lbs) the new (2014) 3 cyl engine is great and a reliable drive train. I have 26000 on mine and no problems.