If your luggage doesn’t get wet out on the rack, all those holes in the lid ought to help ensure the stuff inside the trunk gets wet too!
I don’t have a source for you, suspect you will have to find same model rack that is used and being parted out. Maybe a needle in a haystack?
Possible to use aluminum bar stock and cut, mill, drill, polish. Won’t match chrome 100% but could pass at 10 feet? I guess you could go the last bit and plate up with chrome but even then, new chrome looks different than old chrome with patina.
Not much help, just tossing out ideas.