this is one of the most ridicilous design ideas I have heard in my life! LOL
but if you really want it, why not just open and close the cover yourself?
and good luck in finding a ridiculously small motor.
The only way I can see it done if even that is to use magnetism. Remember in school how you wrapped a nail with wire, and then hooked it to a battery? Yes, it made a short circuit, but the magnet power was good, the nail can pick up other non-magnetic nails.
If you can incorporate this idea in your CD player, you will be set. You will also need a spring. What will happen is that the CD player's door will be open by default. When power is applied to the magnet, the door will close.
Just make sure you do NOT buy a heavy-duty spring or it won't work.