Why not just unplug the USB header if you want a physical solution? The idea that you're shoving glue in there is incredibly ridiculous. You can chip that off easily with your finger or a key. I seriously doubt this is a real story because it flies in the face of published STIGS and basic common sense. Nor would it stop a remotely determined attacker/idiot.

That said, I could see glueing a panel to block them as a visual to remind people that those ports are off, but not as a primary blocking device. More than likely its done via security policy.