I'll bet you can find something. Go to google.com and search for "night sights", "tritium sights", and similar phrases. Somebody's got to be making less expensive sights like that.
I found this when I searched for "cheap night sights":
I use the white nail polish trick too, but I then add a couple of coats of glow in the dark nail polish (Available around halloween) or glow in the dark sight paint (sportsman's guide sometimes has it) works great, just make sure to put the white on underneath it as the glow in the dak stuff is suspended in a clear laquer.