I would stay away from those which are slung beneath the barrel. Any jarring and your point of aim and point of impact won't be in concurrence. Dangerous if you're up against pig or bear (if you can even see it during daylight).
I like both Lasermax which replaces the guide rod for semiautomatic pistols and Crimson Trace which is built into the grip. I don't believe the latter makes a grip for the N frame yet. They've got one for the J frame which is the one I bought.
You may want to opt for a red dot type sight instead. Red dots type sights may be had for as little as 1/4 the price of a good laser with the more expensive ones costing more than a laser.