Anybody remember the Armson OEG? It was one of the better red dot sights available for tactical purposes back in the 1980s. Powered by ambient light during the day, and by tritium at night.
It has been superceded by various reflex sights in recent years, but for close range scenarios (less than 100 yards) the old Armson is still a viable choice...... I've seen used ones advertised for less than $100, just a fraction of what a Trijicon product would cost.