What was once the most common accessory for any rack grade AR, the standard mil-spec carbine handguard isn't the most modular but it is pretty simple and sturdy.
These were previously issued and show some signs of wear, but with a double heat shield these will be suitable for hard use.
You could get a brand new commercial set for nearly the same price, but it won't have that je ne sais quoi of a set of salty handguards that have been issued and maybe deployed.
