I understand your immediate feelings regarding this horrible, HORRIBLE man and his gestures. I also understand that with my being white my suggestions on how to deal with this kind of almost literal CRAP, will sound a bit hollow and lacking in understanding about what it means to be the target of such racist acts.
And of course, I understand that I am speaking from a position of privilege. Absolutely.
So perhaps my suggestions will feel hollow and insenstive to your reality.
But -- also perhaps -- at some point in the future you might feel confident enough in yourself (and perhaps safe enough) to do the RIGHTEOUS Angry Black Woman thing and say something like "Did you just shit out of your mouth and then wipe your butt with it? You are a disgusting human being!"
Or being sardonic and taking a tissue or handkerchief out of your purse and saying, "perhaps this will help you clean yourself up."
Yeah, I know. Probably not safe for you to do. And especially not in front of your niece. I mean, at that point you don't know whether he is capable of committing a PHYSICAL racist act in addition to a symbolic one.
Best wishes for a better world to come for you and your niece and daughter.
Anyway, here's a practical tip for dying phone batteries. There are high power battery attachments that you can use to charge up your phone without having to look for a charging station.
portable chargers and power banks
They carry TONS of power for phones and all other portable electronic equipment. Get two if you want to be really safe so you always have one that you know is charged.