Here is a link for lot's of differnt trailers >>
http://www.workbike.org/makers/index.html I use a Croozer two wheel trailer and love it trailer folds flat when not in use if I want and the wheels can be removed and taken in the store when shopping and is a breeze to use and get used too but a heavy duty option would be the Burley which I wanted but did'nt have the cash ,, most two wheeled trailers are about the same width as your shoulders so don't listen to the crap line about one wheel alway's on the shoulder of the road , a two wheel'd trailer I find is a better option than a single wheel'd one and I have used single wheel'd ones before but I prefer the more stable platform of two wheels on my trailer less strain on the bike and trailer componants ,, it is a personal choice