I do not leave paperwork unlocked. Doing so is an invitation to con artists. Leaving papers in tank bags and such that are easily detachable seems like an invitation to identity theft. License, registration, and insurance card are in my wallet in my pocket in a waterproof envelope. All my bikes are covered with the same license and insurance card, and if you clear your wallet of good-feely stuff you'll have plenty of room for a registration or three, along with spare keys. Cage insurance cards and registrations are locked in the glove boxes.
Boat stores carry a waterproof plastic tube with brackets that is small enough to fit inside even the TW's tiny fairing. I've used Estes plastic rocket body tubes and plastic nose cones with a thin layer of silicone sealer allowed to dry over the mating surface to provide a tight, weatherprrof fit inside a lockable fairing opening. Scuff with sandpaper and glue the tube to the inside of the fairning with silicone sealer.