I need some dump trailers for my business. Where might these trailers be purchased?

Polar King is a great place to buy refrigerated trailers, they offer a wide variety of trailers you can costumize from single compartment trailers to dual compartment trailers.

Big Tex Trailers and Trailers for Less offer good information about flatbed trailers. You should be able to get a good knowledge base from these websites.

Livestock trailers usually have holes in the sides and are used to haul livestock. Stock trailers are typically enclosed completely.

Youtube has trailers.