I have a standard Leatherman Surge leather pouch with the "expandable" nylon side pockets. The Surge and its pouch are about as big as it gets. Don't plan on stashing a flashlight the size of a Fenix in one of those pockets. You might be able to JAM one in there with effort, but it would be not be much fun going in our out - not to mention how badly you would stretch it and wear it out. A small AAA flashlight such as an ARC AAA, Peak Matterhorn, or other such little guy is more realistic. I don't have a photo of the Surge pouch with a flashlight stuck in it, as that is not my usual mode of carry. My little ARC rides in my Nite-Ize pouch which holds my Treo 650. I just did a quick check, and the size of the side pockets is similar between the Nite-Ize and the Surge pouches. Forget about any kind of AA flashlight. Only AAA lights will fit. Also, you'll find that a light with aggressive knurling (ARC AAA) will be a bit difficult to pull out as it tends to grip the fabric. That's why you see a "Grenade Ring" on my little ARC on the photo below (one with ARC AAA & one with Peak Matterhorn). A Mag Solitaire also goes in and out real smooth, but of course it is useless unless modified.
I really like the ARC with the ring - it's kind of fun "pulling the pin" on my little "flash grenade".