I just purchased the best holster for my Glock and it works perfectly with my Crimson Trace Lasergrips. The Safariland 6378 ALS Holster. It has both the "Belt Loop" and "Paddle" options.
It also has the same system as the Blackhawk Serpa, but the release button is hidden and can be activated while wearing thick heavy gloves on those cold winter nights.
I needed a retention holster that also accommodated the Crimson Trace laser grips. I'm really glad I found this holster.