I found mine through Craigslist, being sold by a private party.
If you're planning on towing a car to the car shows, particularly on a trailer, be sure you pay attention to the tow ratings of the units you look at as well as how heavily loaded the rear axle is. It is not unusual to find, for example, a tow rating of 5000 pounds but with the tongue weight limited to 350 pounds. It's also not too unusual to find that the rear axle is not too far from its weight rating with the RV unloaded, and with the hitch so far back the tongue weight gets multiplied by leverage on the rear axle (and, of course, the front axle simultaneously unloaded some). If the water tanks and RV storage space are also towards the back it's not hard to overload the axle in many cases.
Very few class C's in your price range will have tow ratings higher than 5000 pounds, by the way.