Twere it me, I'd hookup up directly to the trailer battery and let the system(s) keep it up to snuff. Much like you'd do in your car/truck. You'd have to monitor the battery output as the HF output would deteriorate as the battery discharged. Or, preferrably, bring along a dedicated battery and keep it topped off with generator or battery charger when hooked up to umbilical.
I've got a battery system at home which powers the HF/VHF units but is charged from ac. Got a Powergate PG405 which does the switching between 12v
power supply and battery and keeps the battery 'smart' charged. Could do something similar in trailer with Powergate/power supply and separate battery. Then, only question is where to put battery and power supply. Hmmmmmm.