I got this
mount to go with a Trustfire that runs a 1x18650. I was skeptical at first, but the light ain't coming out of there unless I pull it out. I doubt you could squeeze a 26650 light in there, though.
I went the flashlight route, upgrading to 18650 cells in the process, because the two other lights that I had (both 3xAAA) weren't cutting it. My light is rated just over 500 lumens, way brighter than the other two combined, but I'm back in the market for a front light. I'm night blind, so I need more light.