A good alternative. Mine fits in my pocket readily but is sufficiently weighted to work well in that context. The blinding strobe buys you at least a few vital seconds to run or to hit back with the device. Fenix makes several affordable, tested, and useful models. Just google Fenix tactical flashlights.
I agree you should not risk pepper spray if you are allergic, however, for most having it in their hand (just as with the tactical flashlight above) means you CAN use it even when you "don't know the attack is coming." I went through a self-defense class and every single student was able to flip the switch (on a non-active dummy water spray unit) and at least use it along with the attached keys against the surprise assailant (four classes that allowed students--even some much older physically unfit participants-- to be tested in different settings including during breaks when they least expected it). These were five-inch slim tubular canisters that like the flashlight afforded a weapon against the face. No self-defense is 100% I'm sure you realize. But at least you won't be shot and killed with your own gun (if perhaps that is your alternative) and in Colorado, this approach has worked against surprise attacks with wildlife--four-legged AND two-legged. Of course, bear spray attached to the belt or backpack when hiking in more risky wilderness areas would be recommended instead, but I digress...