Hi. I just put a Streamlight TLR 2 G on a CORE9. I also have a Trijicon RMR on it. This gives me a green laser, strong flashlight and red dot. If I decide to move the Streamlight on a MP 357Sig I should be able to use the same holster.
Look into the Viridian C5L-R. I posted a write up about my recent purchase and posted it here. Not that expensive, it offers a laser and LED flashlight and it comes with a Picatinny mount for the M&P.