Yeah, there is at least one commercial brand, but the cost is astronomical. I found this vintage briefcase on Craig's List for a very reasonable price, and it took about fifteen minutes to set up. My laptop, in its protective sleeve, fits in the pocket that is attached to the top of the briefcase, so it doesn't rest directly on the bottom of the case attached to the rack. This will reduce some of the vibration, too.
Admittedly, it won't hold my helmet!