Consider the Small But Terrible Pepper Mace Baton
Some people have the wrong impression of small weapons as not being of any use on a big assailant. The truth is even a tiny self-defense weapon can disable an attacker due, precisely, to its size. It provides the surprise advantage because the target never sees it coming, and it is easy to carry and conceal. The Pepper Mace Baton may be the size of a key chain but it can get you out of a sticky situation.
Firstly, the mini baton is really a kubotan, which is an impact weapon that can be used to strike bony parts of the body or poke fleshy parts. Kubotans are legal to carry in the U.S., and unregulated. They are the size of regular key chains, and simple to use.
Secondly, inside the baton is pepper spray. It will cause a non-lethal burning sensation to the eyes and skin, and will constrict breathing, without impairing your assailant for good.