I went down to my local skateboard shop (Push'n Wood) and got a remnant of skateboard tape. Cut it to fit under the trigger and what a difference it made. There's noway that gun will slip out of you hand. I use it whenever and wherever I can.
just a little tip from your uncle Larry (way inside joke)
Skateboard tape works well, but like HKGUY said, does leave a residue if you decide to take it off. The is some stuff called A-Grip that I saw once. Feels like a thin suede and a little tacky w/ sweaty hands, but many like it. I was considering getting that for my USP 45f so the grip doesn't get too much thicker.