Just noticed in my browsing around that Polar also makes the HD Max Trailer. It's a more conventional shaped, rectangular bed trailer with removable tailgate, and 1800# capacity. Supposedly, it's cleaner dumping than the models referred to above. It's more expensive, but looks interesting. Model 10813 is tandem axle/walking arm. Model 10535 is the single axle version.
They are also releasing a hydraulic dump version of the HD Max trailers this spring 2019. I don't know much about these, other than that they appear to be electro-hydraulic. (The hydraulic dump seems to add roughly $1000 to the price).
I've not seen any of these models in person, but they seem like interesting options.