Spec.-Ops

Hello, I am a new member to this forum. I am planning on buying a new Benelli M4. Does any one know if their is a Mag. extender available for the M4? Stock it has a 4+1 capasity. Im looking for a 2 or 1 round extenshion, whatever reaches the full legnth of the barrel. I would also like to find the Mag. extenshion in aluminum with a black finish. Thank you for your help.