When an Electrolaser is not suitable, a Piezo Pistol is the best lightweight form of non-lethal weaponry available. Basically an ordinary slugthrower pistol, a Piezo Pistol uses special ammunition to fire a low-velocity bullet composed of a piezoelectric ceramic material that transforms some of the energy of its impact onto the target into a powerful electrical discharge. This discharge can incapacitate most targets, but the usual disclaimers apply when it comes to the elderly or infirm (who may be electrocuted) or the especially strong (who may shrug it off as just a nasty shock). Supernaturally tough targets such as werecreatures, vampires, ghouls, and some mages may find the shock more annoying than anything. Larger calibers and rifle-style rounds are not generally available, as they tend to have muzzle velocities that render "non-lethal" ammunition kinda pointless.
Behind the Scenes
This snuck into canon specifically so we could write Icarus Hicks out of a corner and give him a way to disable a power-armored trooper using his high Intelligence stat rather than his weak Combat stat.