I replaced the ones on my Golani with the nightsiters dots..... you have to "charge" them under a bright light source for 15- 20 minutes and then they glow for hours. While tritium is better.... the nightsiters are brighter then the tritium's, for the first hour or so.
Oh, and they sell for $10 bucks.... my kinda upgrade!
http://www.nitesiters.com/
P.S. not my company, I don't know them.... ect.