I heard something interesting a couple of weeks ago. Mind you, I have not been able to verify this, so everyone is free to call it speculation if they'd like. However, my source of information is one that I consider very reliable. Anyway, what I was told is that there's only one maker for the tritium vials that go in night sights, which means that the only real difference from one brand to the next is the housing in which the vials go.
FWIW, which may not be much. . . .
I'm a lawyer, but I'm not your lawyer. If you need some honest-to-goodness legal advice, go buy some.