Originally Posted by northhike
That'd be a light....not a laser, but neat just the same.
Click on his link, then scroll down on left side & select 'Smith & Wesson'. Then scroll down until you come to 'M&P'. Shows Crimson Trace Laser Grips which, to my thinking, are better thn a laser hung under the muzzle. They don't cause you to need a special holster & the activation button is usually on the front of the grip, making it a more natural move to turn on & off.
P.S. They show MSRP as $339, but you may be able to find them for less.