A piece of old #poolNoodle can be cut to shape and size to fit over the prongs of a non-folding #USBcharger (or #laptop #powerCable etc).
Once you have the shape and size how you like, you can push the prongs into the foam (not all the way through) and it's set.
If you want it more securely on, add a #rubberBand, #hairTie, #bracelet, piece of #paracord, or such.
You'll protect yourself from the prongs and your prongs from your self :)