I think you will probably have an easier time finding a small residential/outbuilding subpanel type of unit and using a separate standalone converter/charger. There are plenty of standalone 12V distribution panels available; putting all three pieces together is only a matter of convenience for the maker, and so the options with them grouped are relatively limited.
I don't see any good reason to limit your main breaker to 30A. If you have a 50A plug, as I assume you are planning to do, you need to have the lead-in cord and all the wiring between it and the RV main breaker rated for a 50A circuit.
