Tru-Glo makes the Tritium Fiber Optic sight. They are similar to the Hi-Vis, except that they are illuminated for night by tritium imbedded in the sight base.
I have them on two of my XD pistols, and really, really, like them. In the daylight the fiber optic tube picks up a great deal of ambient light. They are the brightest daytime sight I've ever used. At night the tritium lights up the sight to the rear only. The nature of the fiber optic tube directs the light that way without dissipating it through the sides. You cannot see any glow from the sides.
The older version had more liklihood of the tubes sliding out. They replaced my front sight for me that had that problem. Even after the warrantee was over and on at least the second owner, free of charge. The newer generation supposedly has taken care of that problem.
I will not hesitate to put them on another of my pistols when I deem night sights necessary.