Do you know what buses don’t have? Cup holders. Do you know what else they don’t have? Cigarette lighters or USB chargers. Let’s fix that.
Old aluminum box of some sort, some trimming and edging, and some cut holes with 3D printed mounts. Not pictured, but behind the USB ports I also have a 3D printed backplate that conforms to the circuit board and holds it in place. I hate relying on glue or adhesives for things.