If you can't have pepper spray with you then this LOUD 125 db alarm will bring attention to yourself, your situation and startle your attacker.

This small aerosol alarm makes a LOUD 125 db high pitched noise. Not only will this unit notify others that you may be in trouble but you will also surprise your attacker with a loud screech in their ears. Keep this in easy to reach places such as a purse, your pocket or on a key chain.