So far my best find is probably a guy we went and picked up a bike trailer from. He repairs and sells bikes in his garage/back yard. He has hundreds of them, anything and everything from kids to adult, cruisers, MTBs, even a couple of trikes, some bikes with springer forks, and all kinds of other interesting accessories and mods. He probably buys them from yard sales and CL and then works on them, but I haven't bought anything except the trailer so far.