Thanks guys. And thanks for the link, madcratebuilder. I will be looking into those led conversions for the Surefires. I carry a Nitrolon, and that might quite nice!
Here is another idea that came to me. What about a Streamlight M3 or M3X, and a rail mount for the 870. Then, I can carry it on my belt and I could use it on both my Glock and the 870, or by itself if needed.
Hmmm. Any experience with the M3? I use an SL20L for my big light and love it, but that is my only experience with Streamlight.