If I remember correctly, the 669 was a transition model between 2nd and 3rd generations. As such, there would be no Novak options short of major rework of the slide.
I believe there were Trijicon night sights that fit the early 3rd generations such as the 6906. Assuming the early fixed sight (pre Novak) 6906 were likely the same as 669 it may be possible to find a set of those. I have seen early Trijicon SW sights NOS on Ebay.
However, based on the age, even NOS would probably need to be relamped as they typically were rated at 8-10 year life. Trijicon will relamp their sights for a reasonable cost.