Lancer makes a lightweight carbon fiber handguard that's 8 inches.

https://lancer-systems.com/product/lcr5-handguard/

If you want metal, Odinworks makes a lightweight handguard, though the lengths seem to be 7.5 or 9.5 inches.

https://www.odinworks.com/O2_Lite_M_.../f-9-ml-o2.htm


Or just go with Hoser's advice and get the Gucci PRI tube.