Backup phone battery chargers are a necessity. I bought this large capacity one for tailgates. I have a smaller, lower capacity one that's is my everyday purse but this bigger one will be helpful for games.
I bought an Anker E4 recently based on thewirecutter review. So far it's working good, no problems whatsoever. However, it's not solar, and it is quite big. They also recommend Anker for the small "daily" batteries.