Welcome to the forums!
There is lots of good info here.
If you have made it this far, you must understand what the converter does.
The old, original “Univolt”, the name used by Airstream for this box, is little more than a poorly regulated 120 volt AC to 12 volt
DC power supply. It depends on the battery(ies) it is connected to for much of the filtering and regulation of the 12 power it produces.
As such, it tends to supply too much power to the batteries and cause them to overcharge and boil dry.
Newer technology converters have circuitry that makes cleaner 12 volt
power and controls the power supplied to the batteries. They supply lots of charging power when the batteries are discharged and then begin to limit the power as the batteries are charged to capacity.
Some do require a bit of rewiring at the distribution panel to allow them to see the batteries separately from the appliances in the trailer, so they “know” how much power to serve where.
But, there are panels that are easy to retrofit into the factory spaces and are not terribly complicated. If one is capable of installing a car stereo, one is capable of swapping the distribution panel after a bit of research.
Or, there are simple basic converters available. In fact, Airstream uses a basic, simple converter in new trailers.