Posting my findings, and I'll update it as I go.
I found a possible budget ul handguard option for anyone wanting to do a gas gun like mine will still be. I have no idea what original handguard
this was to, but I ordered one and it's OD is pretty close to 45mm. I ordered
this cf tube in 46mm ID and it fits over it with some slop, and it measures that it will be a snug fit with 0.015" shim stock around the nut. I'll probably go with some sort if external clamping and a relief slot in the carbon instead of just drilling for the screws. But for $50 or plus some hardware, my tube cut at 12.5" for the rifle lenght gas my barrel has, it's 5.11 oz for the tube and barrel nut, so I'm hoping to come in under 6 oz for a rifle length handguard and less than the cheapest commercial tubes posted so far. The nut alone weighs 2.5 oz