I priced the 14' Sure Trac dump trailers at a local place called Detro trailers here in Indiana and they have the best prices that I've been able to find by far. It may be worth your drive here. I can give you more info if you would like.
Unless storage is an issue, I don't think you want to use a dump trailer just to haul mowers around. The fuel you save without the extra weight of the dump will pay for that other trailer.