Does it 100% have to be battery operated? Because on a trailer you have the benefit of most likely having a large 12v battery. A lot of the cameras are 5v USB powered which is easy to get from your trailer battery.
Negative to the battery powered cameras is to save on battery life they often have short recording periods. I have not looked around for over a year. But very happy with my Wyze cams. Have had 2 on my toyhauler for a couple years now. Lasted in snow and rain. I do have the outdoor covers and i squirt dielectric grease into the connections.
If you can somehow get wifi to your trailer then it makes for a better experiece being able to check the cameras while away.