Depending on your towing rig, the other way to attack this is to put the inverter in your car near the battery to minimize the high amperage run then extension cord back to the trailer zip tied along the bottom. You could also get really fancy and install an inlet near the front of the trailer that goes to a transfer switch at the panel. Either way, since you're running the long leg at 120V you can carry the same wattage on lower gauge wire with less voltage loss (Same reason the power company uses very high voltages for transmission lines). For the fridge you could even get away with a cheapo 16 gauge cord since it's only pulling 3ish Amps at 120V.
