M4 +2 magazine extension

[inlandparafan]

Hope someone can help......
I would like to buy a +2 magazine extension for my M4. I would prefer a factory tube. Anyone know where I can get one ?
Thanks for any help !!
Inlandparafan

[DAdams]

They are hard to find and if you do find one they cost a ton. Have you thought of just replacing the magazine tube with a true seven round tube?