A shelf for centre speaker

This may not be the right place for this, but here goes.

I have recently wall mounted my panasonic 42" plasma using a universal wall mount from avsales (the non-tilt one which was on offer).

I would like to find a shelf for the centre speaker which would hook onto the wall mount behind the tv and hang down so that the centre speaker can be placed on it, without having to drill a hole in the wall and wall mount the centre speaker seperately.

Does that make any sense? If not, I could draw a picture i suppose!

Rossicha