I bought these together and am beyond pleased how it turned out. I've had my eye on getting a laser for a while and realized that none of my holsters would work with something left attached to the rail. I did some research and found this Fobus holster made to hold a pistol with attachments.
NcStar green laser attached to the Picatinny Rail with a Fobus holster designed to hold pistols with attachements! Shown here is my Beretta Px4 Storm 45, but it also fits my Springfield XDm. The holster has a small post that inserts into the barrel, then the plastic grips the frame like a firm handshake. Lastly, the wrap-around snap protects the trigger and keeps it very snug and secure. You can draw very fast with this design too.