The OnGuard Akita cable lock is a low cost option for securing your bike when for short visits to the shops or cafe. Akita is a lightweight and flexible bike lock which you can easily carry in your pack or on your frame (vinyl coating prevents scratching).
Cable locks are more versatile and flexible than D-locks so are great in low to medium crime areas. The cable allows you to fix your bike to trees, lamp posts and other awkward places.
The M-Wave F 720 Folding Lock is a unique heavy duty lock that folds up to fit into a pouch that is 4.5 x .4.5 x 2 inches. Truly secure.