Some good info that's already been offered is an action job by a competent 'smith. As noted, though, smooth is more important than light, and there are definitely limits to how low you can go, so be sure to test for reliability.
Someone mentioned getting more of your finger on the trigger - that can help, and radiusing of the trigger face and installing grips that reduce the distance to the trigger face can help in that regard. I find the SP101's trigger face to be particularly sharp, so any SP101 I'd buy would get a radiusing whether or not it got additional tuning.
The trigger mechanism of a revolver is largely about levers and leverage. Generally, smaller revolvers have smaller levers and therefore less mechanical leverage, so their trigger pulls generally tend to be heavier. As such, a bigger frame (S&W K/L), while not as light and compact to carry, often have a wee lighter pull weights, and can be tuned more aggressively as well (and hold an additional round). A good gunsmith can likely get a S&W K/L-frame down to 8.5-9lbs and reliable with factory ammo.
Finally, if you're only shooting DA, consider bobbing the hammer and converting to DAO as part of a good action job. All else equal, bobbing the hammer actually enhances reliability, so you can tune the revolver's trigger a bit lighter before you get into reliability issues.