The Shad comes with a "generic" mounting bracket for it's case. Yes, Givi makes the Honda top box.
I tried a Shad before I went with a Givi. It was a nice case, but after getting everything together, I found the locking latch was broken... there was some other little nits I wasn't to happy with. I was able to return it for a full refund since it was damaged. I'm not so thrilled with my Givi either, the locking latch will not lock all the time, and when it does, sometimes you can just pull the lid open.
To me, even though the Honda case is made by Givi, it seems it had a better build quality... just something to think about.