The best tactical light for a TRR8 is a Surefire 6P or equivalent, which fits by itself in a holster on your left hip.
A barrel mounted light is not practical to use in a typical self-defense situation. It takes two hands to operate (one for the revolver), and it's not practical to mount a remote switch. You don't want your hand in front of the cylinder when it goes bang.
I use Crimson Trace grips for SD revolvers. Their operation is intuitive and they fit in any standard holster. I've had better grips, but the rubberized CTs are okay, and not too sticky for concealed carry. If you sight in at 50' or more, the offset can be ignored.