Assuming you're referring to the forend/hand guard, not a vertical forward grip.
I use an Odin Works forend on my DPMS pattern AR10. It's light, free floating, flat on the bottom and well-ventilated.
https://www.odinworks.com/category_s/1907.htm
Lancer systems make a crazy light, and stiff carbon fiber one
https://lancer-systems.com/awc/product/lch7-handguard/
JP rifles has a pretty solid reputation for a great product- I've used them and like them
https://www.jprifles.com/1.4.4_hg_mkiii.php