This baby right here:
Tritium RN Front Blade : AR-15/M16 HIGH VISIBILITY ROUND TOP TRITIUM DOT FRONT POST SIGHT | Brownells
It fits in the standard GI fixed front sight and also in the Magpul BUIS. Less than three months old. Silkscreen Trijicon markings on side are wore off from sight tool twisting but otherwise it's perfectly fine and presents a large glowing dot to shot from. Comes with tool shown. This isn't for target shooting (full turns only) but would be great for SHTF and HD.
$40
Tritium RN Front Blade : AR-15/M16 HIGH VISIBILITY ROUND TOP TRITIUM DOT FRONT POST SIGHT | Brownells
It fits in the standard GI fixed front sight and also in the Magpul BUIS. Less than three months old. Silkscreen Trijicon markings on side are wore off from sight tool twisting but otherwise it's perfectly fine and presents a large glowing dot to shot from. Comes with tool shown. This isn't for target shooting (full turns only) but would be great for SHTF and HD.
$40