The best picture I seem to have is of a Colt R6530 Sporter Lightweight as follows...
The arrow I marked with the letter "A" shows the raised reinfored area on the lower receiver that I am refering. This is the area that gets drilled for the pivot pin spring and detent which hold the front pivot pin in place.
Please note that Arrow B points to a Mil-Spec push pin as this lower came with the hole drilled and a Colt's funky 1-headed screw. All I needed to do was buy a mil-spec pivot pin, spring, and detent and put her together!
The best place to get these parts is JUST ABOUT ANYWHERE! I think these parts as shown are Bushmaster Parts but I know I have also bought these same parts from Armalite for another gun! They are all basically the same!
Also, I just realized that I almost cropped off the pin that holds the Sear Block in the lower. Look at the left side of the image! Colt has several varieties and I know some guys don't like the huge pin, but I don't mind it!
This gun has all my top choices:
1. Small Pivot (Push pin at that)
2. Mil Spec Trigger
3. Black Color
Good Luck!