I spent a great deal of time researching a rack for my Gen III.
I was not able to find any after-market support in the USA for a roof rack that bolts up to the factory mounts in the roof. There is support overseas, however the shipping is crazy, as expected.
I finally decided on a BajaRack. It mounts on Yakama cross bars, which mount to the factory rails. I've had the thing loaded with only two cross bars and it's held up! I've thought about fitting another cross bar, but haven't made the time. It rides a bit higher than I really wanted, but the cost of a custom fabricated rack that bolts up to the roof was out of my price range. If the future, I may fabricate brackets to attach the BajaRack directly to the factory roof mounts.
One thing for sure, the extra space is mandatory for expeditions with the whole family.