If you can not find a used one there is always the possibility of buying a new trailer. The cheapest option is one of the boat trailers from Harbor Freight. You have to put it together but it is very simple to do. I have built/owned two of there boat trailers and currently use one of their utility trailers, there cheap but functional.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5002