The creatures in question will also tend to avoid any areas where lightning or similar electrical discharges have gone off for a few hours, as for some reason, if they enter that area within the stated time, it burns their skin.
Ozone generators.
The electromagnetic radiation is long gone. What remains so long after is the result of the energetic discharge: free radicals. One of the main ones is ozone. It is produced by lightning dissociating oxygen, which recombines as an oxygen radical.
I can imagine ozone burning a sensitive creature. Ozone is commercially used for exactly that: oxidatively destroying odor causing molecules and also pathogens; ozone has taken over the role of chlorine in sanitizing swimming pools.
Your creatures don't like ozone. It is easy to generate ozone. I would marry an ozone generator to a vortex gun and shoot these creatures with ozone-containing vortices.
Riffing a little more — there is nothing that special about ozone except it oxidizes and electricity makes it from the air. But if your creatures are that sensitive to oxidative damage you might experiment with other oxidants. You could fill a supersoaker gun with hydrogen peroxide or bleach. Try that when you have your wingman ready with the ozone vortex and carbon arc light if it doesn't work.
Fricking Lasers!
Seems like a no duh. They are very bright and energy efficient. And awesome. You can carry many, in a bandolier. As a light weapon they offer obvious advantages over a flashlight. Best of all you can get a giant array from a rock concert laser light show and blast monsters to sweet rock and roll. Fog machine optional. Dancing non-optional! Dance that night away!
