Martus

So I got an M3 and am pretty surprised at the lack of modding options for the forend. I've seen the odd photo of people putting angled grips or rail on the bottom of their forend (like in the photo), but finding information about this is pretty difficult since everyone seems to own an M4. I've also seen the M-LOK Toni System forend, but that one only adds the ability to attach something to the sides. So is there a rail or a grip I can add to my M3 forend?