This is one of the few gun accessory ideas that doesn't really depend on money. You can get the very best quality and spend a lot of money and not overcome the basic flaws with the idea of using a laser on a handgun. A light has a lot of virtue, but a laser? No!
First, a real life story. No, I swear it's true! A close buddy was sent to Iraq right after the 1st Gulf War. I wanted him to have all the advantages he could so once he was there and told me the environment he was operating in I sent him a combination light/laser, and what was then the most advanced reflex/holographic sight, the EoTech, both for his M4. This guy is a very serious operator and used these to good effect while there for 12 months. After that experience, this was his opinion of each:
a. EoTech. Battery life too short. You don't have time to constantly adjust the reticle's brightness when you are in a firefight, especially when you are going indoors and out rapidly. Reticle too crude for distance shooting with accuracy. We went with a 2X Leupold scope after the first deployment.
b. Light. Superb in every respect. Very flexible and adaptable especially when using a tape switch. Use it when you need it, but otherwise keep it off.
c. Laser. Superb for intimidating the enemy or suspected enemy. Putting a laser dot on someone's chest has a way of defusing the situation. Also very handy when designating fire at night, but less so during the day since the dot is largely invisible in bright light past 30-40 yards. However, relying on it to help you aim your fire is a waste of time. Dot is too difficult to acquire initially, or reacquire after each shot. Looks cool in the movies but has little real world application.
I'm sure there will be comments that claim the exact opposite of what was just said, but hey, that's what makes a market economy function...different opinions.
b.