There's an old joke about teaching a pig to dance...
Really, if this person won't carry or even use a loaded firearm, I highly doubt he/she will have the mindset or will to carry & use OC spray, EDWs(tasers) or any other self defense device/product.
As I've posted on firearm/tactics forums & message boards in the past; Guns are not props, toys or fashion statements.
Sit down and openly discuss your concerns with the person. Be aware of the legal, moral & social issues too. Know your area's use of force & defense laws.
My state does not allow private citizens to use more the 4oz of chemical agent(OC spray, Mace, pepper spray).
If the person DOES feel they can safely carry a defense weapon or wants to follow the local-state laws, check here; www.Taser.com www.galls.com www.policehq.com www.uscav.com www.qmuniforms.com
A C2 Taser could protect a citizen in most events. I now use Sabre Red Mk III on my security details. Fox Labs, First Defense, Mace, Galls have good chemical agents(stream, foam, fog, etc). Make sure the OC spray doesn't conflict with energy weapons(Tasers). Flames or sparks may iginite. Yes, it's not a MythBusters bit. LE agencies & security officers have been sued or faced civil lawsuits over it.
Have the person train, document the formal training(with a respected, licensed program) and avoid the cheap gun show or mall ninja $&@#.
Stay safe & stay legal;