Yeah Mirador is right, dont waste your time. Even with mace, if you dont fire it off just right and hit your opponent where you need to hit them, or close enough, you wont stop them. You need to keep a cool head and act deliberately. That requires practice.
A much better alternative, frankly,is an old fashioned "sap." You dont aim for the usual places, any attacker will be prepared for that. You kneecap them. Even a tiny bit of heavy lead applied with the flick of the wrist to the very vulnerable kneecap or shin bone will stop an attacker dead in his tracks.
Ha! I know it sounds funny, but it does work. However, like all forms of self defense, it takes practice and a bit of training.