I bought a PortaPow Fast Charge + Data Block USB Adaptor. Apparently it may improve charging USB-powered devices, but I got it because it blocks data over USB. The SyncStop does the same thing, but I don’t know where to get one of those.
This will be a very handy little gizmo to carry around. Sometimes I need to charge something over USB, but I don’t trust any USB port that isn’t my own. And sometimes I don’t even trust those.