I had someone build me one... I guess it could be considered a one-off or a DIY.
After seeing the process I think I could have did it myself if I used the roof with the factory rack removed as a jig so you can clearance the roof correctly.
To be honest I kinda want to change it out or build another one that doesn't have any light bar mounts so its flat from end to end.
We used steel, and I would re-build it with aluminum if I could. The weight being placed in the highest location is noticeable at highway speeds.
Build a wind faring... it's very necessary at highway speeds. From a noise and vibration standpoint, it can make driving without very annoying. You can even feel & hear the cuffing of air on the roof
Not the best picture, but there are some spacers and diy gaskets made to elevate the rack from the channel in the roof, and a gasket cut on both ends to help weather proof.
I can take better pictures later if needed.