[tentcamper]

What I ended up doing to get the second heater off the one 120V outlet breaker. I installed a GFI outlet on the AC unit junction box.

Under the camper below the water heater is a junction box that connects the rubber cord that powers the AC unit and is wired back to a 20 amp breaker. It's a 20 amp service. Since I don't run the AC and a elec heater at the same time. I mounted a 20 amp GFI outlet to that box with a weatherproof cover. Now all I do is drop a white 4' extension cord under the flap to the box.

When its cold and we need two heaters. We use that heater for the front section and keep it on high and the second heater we put on low when using appliances. The second heater we use a plug thermostat to maintain temp.