The USB charger for my Android phone was a close fit, but not tight enough, so I altered the hole a little bit to accommodate my charger (I have no idea where I got the charger - it's labeled Quilcell on the back - see photo). Then I moved the webs away from the tray a little bit so I could loop the excess USB cable around one of them to keep everything off the floor.
I've included a STEP file for anyone who might find it useful.
outlet-shelf.stl | 776.9KB | |
outlet-shelf.stp | 352.9KB |