XL cruiser cover doesn't fit well so you'll probably have to go with a touring bike (I.e. Goldwing / HD Ultra) cover. As far as helmet locks go it depends on the type of helmets and how secure you want them. The cheapest and easiest way to secure helmets to your XR is with bicycle locks (wimpy plastic covered chain w/combo lock). 1/2 helmets can either fit in your bags or hang from handlebar ends with the chain going through the side straps and the trees. Full helmets can sit over your mirrors with the same chain arrangement or on the seat with the chain through the bag mounts.
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.