Well since the G-26 does not have any rails like the XD9sc does, you're going to have to go with a light which mounts to the front of the trigger guard with some sort of clamp and screws.
I did a quick search online and didn't find any white light illuminators in that configuration. I'm sure they're out there, they make several lasers set up like that.
That's one of the reasons I went with the XD when getting a sub compact pistol, although I haven't gotten a tac light for it yet. I do have an Insight M3 light for my G-23 but the sub compacts take a smaller light. I believe it's called the XM-1.