I bought a very compact 150 lumen light from CDNN. The brand was "Target" but it is identical to the NC Star. It has a quick release lever that attaches the light to the rail and is easly transfered from gun to gun. The best part is that it was inexpensive and is super bright!
Have you mounted it to the sr9? I tried a Streamlight Trl-1 and while it fit snugly on my sr9, the toggles were just a little to far for my trigger finger to reach with out changing my grip position. So i guess I'm looking from other Sr9 owners if they have found any solutions for mounting lights that fit well.