Hundreds of Ar15 parts from Strike industries available. 

Black 8.5" Ar-15 m-lok rail
https://www.strikeindustries.com/si-gridlok-bk.html

B
lack and Red Ar-15 m-lok rail 15.5"
https://www.strikeindustries.com/si-ar-strikerail.html

-Link Curve angle grip 
-Buffer Tube
-Charging Handle
-Selector Switch
-Baseplate extension 
-Magazine Catch
-King Compensator
-Mini King Comp
-J-Comp