Evil Spirit Greaves can be received after completing the Side Quest "The North Lomei Prophecy". First go to North Lomei Labyrinth to get the challenge, then complete the maze. When you defeat the Flux Construct (Hard), and complete the quest.
How To Get Phantom Ganon Greaves Back
Available From The Bargainer Statue In Depths
Once the Phantom Ganon Greaves is obtained, it will be available in the Bargainer Statue lineup in Depths, and can be reobtained in exchange for Poes. The Bargainer Statue lineup will be restocked during the Blood Moon, so as long as you have Poe, you can get it over and over again.