I research here and Lewster the commercial member recommended two brands, Progressive and Southwire. They are essentially the same and both good products with "lifetime warranties. What made the difference for me was Southwire has a wireless remote monitor that can be monitored inside the trailer. I didn't like having to go out to check the EMS at night, bright sunlight (hard to read), or bad weather.
The monitor is 3" x 4" with a decent sized screen and mounting bracket. I just got and haven't had a chance to try it yet. In my conversation with Progressive, they didn't have a remote monitor with the portal unit.