You can find the Ce'Tennan Oculus in peculiar space anomalies (the blue swirly things on the navigation map). These anomalies are somewhat rare, but they can appear in any system. They're always level 6 encounters, so come prepared!

The Oculus can also rarely be found as a quest target for randomly generated quests obtained from NPCs in any village.

If you want to spawn one in, the ID is "centensguardian".