Welcome to the forum.
You might want to try a local gun show for your pistol sight.
A gun sight has to be built a lot stronger then a regular laser, due to shock waves and excessive vibration.
It also needs to be waterproof. (hunting)
Most important is to get a 532nm (green) laser sight.(which is what you said you wanted, anyway) The 650nm (red) is useless unless it's almost dark out.
In my area (FL.) you can get a good Ncstar green sight W/ squeeze actuator (for the grip) for around <$75. For a military spec. one, expect to pay >$200
If you buy a regular laser and mount it on a pistol, it won't last 10 minutes. (unless it's going on a heavy .22) IE: Ruger MKIII Hunter,etc.
My favorite one is Lasergrips, replacement grips W/laser built in. I have them on all my concealed carry pistols, it doesn't add mass to the pistol. or snag points when you draw. (not cheap although.)
Take your time and find a good one.