I've sifted through many CZ accessory sites and have never come across any nights sites of any sort. I see two possible solutions that might suit your needs:
1) Try and find some of the fiber optic sights that were produced by NEA a year or so back, or...
2) get your self some glow in the dark nail polish (or something similar) and apply dots to your sites.
No one has produced tritium sights for the CZ-858/VZ-58 rifles from what I can tell. If they have they are rarer than a hens tooth.