I got a small hardened key lock from Ace Hardware. I think it was about $6.00. They also sell aircraft cable complete with thimbles and nicos. I have a nicopress so I got about 6 feet of the cable and built it up using the thimbles and nicos at either end. Total was about $11.00; its light and packs up easily in the side pocket of my framebag. Its only meant for broad daylight in tiny little towns where everyone knows everyone else and I'm only a few minutes for resupply at a gas station or grocery store (or a restaurant; if its a hotel I take the bike into the hotel room). Just 'keeps honest people honest'.