It's been almost a month, but if you're still looking for suggestions, the stream light tlr-6 and the surefire xc1 are the most compact pistol mounted lights. Ideally you'd carry a stand alone light so that you can get illumination without necessarily having to point a gun at whatever you're trying to look at. But I understand that space availibilty on one's waistband and in one's pockets can be limiting.
A lot of the stuff saying you need a weapon mounted light is in the context of home defense or overt combat. In those situations, it's a reasonable assumption that you might have your gun out before you have positively identified the perceived threat. At which point a weapon mounted light becomes essential. In the context of concealed carry, your gun really shouldn't be coming out until after you've positively identified a threat. So then if the light serves no purpose in terms of identifying the threat, it's reduced to "just" being a light to help improve your shooting in low light conditions. The question becomes whether the added bulk of a light is worth the improvement to your ability to shoot in the dark. I hope my long-winded reply makes sense and is helpful.