Eufy does sell solar panels for all their battery cameras. If yours has a built in solar panel I’m not sure if you can add a separate panel you might want to tell the community what camera you have and ask if you can add a external one. There is a help phone number in the app at bottom of settings you can call Eufy support I’ve had good experience with them. If you’re on hold for a couple minutes they come on with a message offering a call back from next available and they do.
I just did a google search if you can add a external panel to a eufy camera with built in panel and it said yes but you should google it yourself anyway