Order any 'carbine length' (around 7 inches) handgaurd/quadrail. Warning: the ones that are 'free float' will require you to remove the flash hider,gas block,and delta ring or barrel nut. There are you tube videos that will show you how to put it on and it's not hard at all. You can spend as much $ as you are willing to on mods. Here is the one I have. http://www.amazon.com/gp/product/B00...ls_o00_s00_i00
And a pic.