In to clear up the usual misconceptions about tritium before the thread gets too messy.
The half life of tritium is about (just over) 12 years. So after 12 years it will be half as radioactive. That doesn't necessarily mean the phosphorescent tube containing the tritium will appear half as bright though. There are a huge number of variables. Firstly, there will be a point at which there is 'wasted' radioactive decay as the efficiency of the phosphorescent coating will depend on the amount of alpha decay, so the actual brightness emitted may not be 50% after 12 years. There is also the fact that some of the tritium may have escaped. A very very small amount. Then there is the fact the phosphorescent coating will likely deteriorate as well. And then we have the fact that we are interested in how the human eye persieves light and not how much actual light there is, and this will depend on ambient light, how well adjusted your eyes are, and a host of other biological factors. All of this means that after 12 years, you will perceive the tritium tube to be somewhere between 25% and 75% of the original brightness, and that percentage will be different for different manufacturers and in different ambient situations and contexts. Anyone trying to give a higher level of accuracy than that is making some large assumptions.
Anyway, I don't know of any current options except tritium, and variations of luminous paint which need to be 'charged' and which decrease in brightness the longer they are in the dark.