I don't know about aftermarkets, nor have I taken a look inside of one to see just how it works...
But, it looks somewhat similar to the trigger in the 917; it can be pulled out by just tapping out one pin. In the 917, you just take it out and replace the spring with one from a Papermate pen to drop trigger pull down to roughly 3lbs.
Pull your trigger out and take a look; if a spring comes out with it, find a similar sized one or cut one down from a pen and replace.
For more intensive work, those wiser and more experienced than me would be better; stuff about polishing metals and the like. Pen-spring trick was all I needed to make mine a laser, though.
