First of all, you didn't need to post this in multiple sections.
Secondly you may wish to clarify if you are looking for a real one or if an airsoft clone will meet your requirements.
Finally, if you are simply after a clone, a quick google search would yield you the answer to your question.
I realise this may sound harsh and unwelcoming but this is a very easy query to answer with the most basic of research. Of course if you are looking for a genuine one then it becomes a more complex question as it relates to military equipment which is currently in use and typically isn't seen in the surplus market. To be honest if you're after a genuine one I doubt that it is actually legal for civilian ownership/use.