Heavy duty FrontRunner platform roof rack. (Now Dometic) Mounts on topper or roof of a car or truck or just about anything else you could think of. It doesn't come with the tracks but they're easy to get. $1300.00 New. Compare here.
https://www.dometic.com/en-us/product/are-canopy-slimline-ii-rack-kit-1425mm-w-x-1560