C-12 Dragonfly drone. Minidrone with a heart of high explosives. Exactly what your guy is looking for, just comes in swarms and can steer them yourself to ignore ECM, also, they are about the size of a real dragonfly. Pack the punch of a standard HE grenade.
SR4 has nanotech. How would it not have the tech base for small guided missiles when you have drones the size of bugs? Hell, ditch more of the whole drone thinky shit, give it a simple guidance system, and stick on a larger warhead if you want.
For more fun, buy them in mine loads and unleash hell.