How to obtain more Crystocrene armour pieces?
High value targets drop either the Crystocrene armor or the weapons from Europa. You can double dip on the chest by sparrowing outside of the area until you switch zones, then going back and opening the chest before it despawns.
Also, as Wondercricket said, the first daily Heroic public event in the Eclipsed Zone, while having the sabotage upgrade is guaranteed to drop armor.
You can also farm Empire Hunts. The harder they are, higher the chance for the armor to drop. Good luck.