I just spent months trying to find such a trailer in Ontario. Good luck. I finally gave up and ended up spending a lot more on a gooseneck instead. However, you are much closer to better deals than I am, so if you are persitent you will have better luck than I.
Best advice I can give you is to religiously search Kijiji for all of Ontario within your price range (actually go a bit higher for the "dicker factor"), and set the distance appropriately (350 km?). Other sites I checked were horse trader classifieds, horseweb classifieds, equine.com, horsetopia, horseclicks.com, buysell.com, equinehits.com, freehorseads.com and canadianlisted.com. We have the bargain hunter in my area also and you might try one of the autotrader.com sites -- farm equipment maybe?
Auction sales might be a place to go -- lots in Southern Ontario.