How can portable solar supplement Pebble rooftop solar?

My Pebble rooftop solar is working just fine, but flat rooftop solar on a trailer will always be limited at higher latitudes, in shaded campsites, and during shorter days seasonally. I’d like to have the option of plugging in portable solar panels to supplement the rooftop solar. I added such to our Airstream, but that was simple wiring compared to this computer-controlled Pebble. Has anyone thought through this?

A simple option would be to use a power station, such as the EcoFlow Delta series, which could accept solar input and feed the Pebble through the existing charger, simultaneously charging with the rooftop solar. That’s one more piece of equipment to carry, however.

Any ideas?