its not so well developed in production because non of the company would waste their money off on making something useless, if they are useful, im sure every law enforcement over the world will had them issued on every personal already.
honestly, stun-guns are horrible as a self-defense device, one of my buddy got his wrist almost cut off by an assailant when using it to defend himself from a machete welded mugger
the reason why, its because you need to get it extremely close to the target in order to make skin contact with the electric shocking bezel which is something stupid, as a natural reaction, the attacker would just grab your wrist and take it off from you, probably use it back on you, might end up even worst than you expect.
get a good, effective OC pepper spray, if you do care about her life, seriously.
if you still wanna stick around electric based weapon, get a Taser C2 or similar device that works in range without closing up to the attacker especially for untrained personal.
above shows a flashlight styled stun-gun, and a taser with a spare round on below.