My answer is "none." If you are looking for a less lethal response, your best bets are a good high-intensity flashlight and/or OC spray.
If someone gets close enough for me to hit them, they are close enough to hit me. And at 68, I'm too damned old to get into a physical confrontation with anything less than a good club. (I do medieval martial arts in my off time and can do a lot of damage with a club).