I will have to add a +1 for the mini mag. I have the same one I used over seas. it has been great and not very expensive. But also it is like someone else said when you buy the Surefire you get what you pay for.
I am a proponent for a weapon light. I know you said you wanted one for weak hand carry. But a Surefire x-300 on the bottom of your handgun is the, I feel, best way to go. It is also my belief that all your home defense guns should have a weapon light on them. But at the bare min your HD handgun. Having that spare hand in an indoor combat situation is vital. There are doors swinging, stuff you must constently push away or move, and Reloads.
Having a flashlight readily availible is always a must, but if your intent is to have light for the instance of fighting a weapon light must be in your equation.