This solar panel from Amazon (ALLPOWERS 2.5W 5V/500mAh Mini Encapsulated Solar Cell Epoxy Solar Panel DIY Battery Charger Kit for Battery Power 130x150mm (Solar Panel Only)
Will charge a GoTenna mesh node during the day, enough for 24 hours. The GoTenna draws about 270mA when charging, and this solar panel can easily source this.
I put a 5.1V 5W zener diode across the panel
In case the mesh didn’t like the full 6V open circuit voltage of the panel.