What ever you decide, don't get an airsoft specific light (UTG / King Arms etc). They're trash. If you need a light for room clearing when you go from bright outdoor conditions to dim indoor conditions (and especially if you have smoke lenses), I'd humbly suggest getting a rifle (primary) mounted flashlight.
Now, you can actually get a TLR1 / 2 (or if you want to show off, an x300), which is shaped for a pistol, but still mount it to your rifle rail. This gives you more options than if you went the other way and got a weapon light designed for a rifle mount, since you can't put that on a pistol.
Plus you won't have to find a holster than can accept lights - you can just (for what ever reason) pull off the light from your rifle and put in on the pistol if you need weapon maneuverability.
Heck, you could even *make* your own holster for a light bearing pistol. Just get some kydex, look up some videos on youtube, and you can make your own holster for any pistol.