Look at AmeriGlo, Trijicon and TRUGLO. Select what you like and buy them at
OpticsPlanet at a discount. Using the code JYTR5 may get you another 5% off.
Understand that night sights are good to have, but also overrated. A flashlight is more important than night sights. If you can't see your target and positively identify it as a threat, then night sights don't help at all. Certain flash light techniques backlight the sights, so you would not need night sights for that. You will be point shooting at anything in contact distance anyway, so you would not need night sights for that either.
Night sights are good for low light conditions where you can positively identify the target (without needing a flashlight) and you need to (or should) line up the sights. In this case, they do not need to be incredibly bright, but should be clearly visible.
Tritium sights are limited in the amount of brightness they have. Fiber optics sights can be brighter
under certain circumstances, but can also be too bright in daylight.
I have the AmeriGlo CAP sights on my S&W M&P Shield 9, see the
Good Bye XS Big Dots discussion thread on why.
OpticsPlanet has them for $75 (see model
SW-618 at AmeriGlo).