Here's something I worked up last night. A super simple tac light mount for my PPQ. The flashlight is one of those free w/purchase deals from Harbor Freight, so quality it is not, but it seems to work well, though granted I haven't shot it yet. The flashlight floats in the mount, so I can push it into the trigger guard to press the button. The slightly larger OD of the knurled sections prevents it from working it's way out under recoil (hopefully).
The mount itself is two pieces, with a middle section that interfaces with the accessory rail of the PPQ, and the screws go through it to prevent the mount from moving. If I tighten the screws too much it binds the flashlight so I may need to widen the middle section to prevent that, but otherwise I'm happy with it.