Top box, Givi, Shad or maybe something else?

[Nachodaddy]

Right! So much depends on how the box will be used. When he said it should hold two helmets, my first impression was that he wanted it to store the helmets when he and his rider got to their destination, not so much as when riding. Having it full and carrying a passenger is an entirely different story. But then, there's no place to hide the helmets when you stop at the pub for lunch.