On my V-Star my left side cover has a lock on it to secure my tool kit. I RTV'd a zip-lock bag inside the side cover and keep my reg. inside it. The same thing will work on the Cross bikes but you have to be a lot more careful with the side cover. It's tough getting them off without hitting your passenger pegs/floorboards.
Or you can put your reg. in the bags, inside the tool kit; the bags are huge -- it won't take up much room.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.