Some derivative of an X-26 is an effective option, or another capable taser (NOT a stun gun.) Even if someone is hopped up on drugs, it doesn't really matter as these things could stop a freight train. It is easy to use and in many cases will incapacitate even faster than handgun rounds. I took part in a workshop and once that current passes to your body, you freeze up to a board and lose all physical control. Your mind tries to tell your body to do things, but your body doesn't. You think you are screaming, but you actually aren't making noise. Despite what the movies constantly show, this isn't something one can fight their way through. If you do volunteer, you will want to use the bathroom beforehand and have a change of pants available. Like other LTL, people die from tasers on a regular basis, but the overwhelming majority of people who are the unlucky recipients do not. Many deaths from tasers can be linked to certain health conditions/issues.
Key chain kubatons can be used as a close range impact weapon. When put on the same keychain as an OC spray, that's a wider range of distance in which a response can be employed. Some folding knives are also designed to be used as a close-range impact weapon when closed.
The karambit, while not always non-lethal, is a very effective means of self defense when coupled with an understanding of correct usage. Emerson's folding karambit is very likable due to the compactness and blade grind that tends to perform well with defensive weapons. It's worth noting that if you disembowel someone, even if they survive there is a good chance that you may be facing as many or even more legal issues than you would for using lethal force with firearm.
