I carry the same setup appendix and I went with a Trex arms light compatible raptor holster. Opinions of the owner aside, my reasoning was that it appeared to have the smallest footprint for a holster that accepted an x300. The retention isn't great, and definitely no positive click like I get with my Raven concealment phantom light compatible. It will hold the gun and light while upside down without falling out but if you shake it around the gun starts to come lose.
I previously carried my G19 in a Raven Eidolon, and the Raptor holster is about the same footprint but with the x300 sticking out. I can't post pics on here, but I'll email you a pic of the eidolon sitting on top of the Raptor for size comparison if you're interested in seeing it.
LeeWall, Why the distaste for the Raven Eidolon? I have been looking at that one for both my G19 and G43.