Safariland 6360 0r 7360 for the G19 w/ TLR/X300. These holsters (at least the 6360) index off a peg in the muzzle instead of the light.....the weapon can be secured without the light, so if your light is a little small, it shouldn't be an issue.
You ought to be able to lay hands on one and try it out, if you've got any stocking police gear stores nearby.