Back in the day, Lonestar was one of the few companies out there making any furniture for the AR15. They made two types of round A2 style handguards, one with an end that would work with the triangular cap, and one that would work with a round cap. I don't know why they made the latter as you had to remove the triangular cap and replace it with a round one. A fair amount of work for the inexperienced gunsmith just to switch to round handguards. They were the only option if you couldn't find real A2 handguards which were scarce in the beginning.
The handguards did have liners in them and seemed to hold up well under heat. The grip they offered was a fat A2 style with a trapdoor in the bottom. It wasn't very well designed and the door would often fall off.
Choate was one other company that offered AR15 furniture. They made a neat clubfoot stock that allowed you to tuck your off hand underneath the stock when firing from the prone or a bench. They even called it an off hand notch.
Ramline made an A2 style grip that sucked worse than the Lonestar. It had a neat little sliding cover that would slide right off the first time it went to the field.
While grips offer a space to store items in, I wouldn't store anything of value in it as it was most likely going to be lost during the first half hour of the patrol. I wouldn't cry over a pack of chewing gum but a spare parts kit would certainly be missed.