The bigger problem here is I don't think there is anyway to directly charge the bike with a solar panel. You are going to have to use the bike's charger and it require 120v and whatever amperage to work. You would need something along the lines of an Ecoflow River powerstation thing and then use solar to charge that.
https://us.ecoflow.com/products/rive...41636514136137
If you are handy yoy could rig something up with the solar panels on the bike you could charge the Ecoflow while riding at least some.