I don't want to pay for uber to return my charger
Why don't you want to pay them?
I think they should just bring it back to me.
Even though it was not their fault, they are trying to do something good for you by returning your charger. It would not be nice of you to be rude to them.
They aren't doing anything for me though.
You can't claim someone else did something when you were the person who forgot it. You should be appreciative they even found it and didn't trash it. You should say thank you and pay them for their time.