Don't rule out the bubble cover just yet.. It might fit, depending on the size of the wall wart.
I have used bubble covers with wall warts before, in places where I needed the wall wart to remain plugged in.
For instance, I used one in the bottom of a podium. A bit of hard foam to fill the space between the wall wart and the cover serves to keep the wall wart from falling out as the podium is moved, and the cover prevents people from trying the use the outlet, as opposed to the other outlets provided. I might have used a single receptacle in that example. It was a smaller wall wart for a Littelite.
