The Jade Ixupi is an unseen Ixupi, since it was encountered in events prior to the game. One can only speculate on it's appearance.
Possible hiding spots
So far, the only confirmed hiding spot for the Jade Ixupi is a Jade Skull that had originally been displayed in the main hall of the museum. The skull is later discovered in the Funeral Rites room, near where Merrick's body is discovered. Most likely, Merrick had planned to use the skull as a defensive weapon, not realizing the Jade Ixupi was in it.
The vessel the Jade Ixupi had been imprisoned in is found in the
Fortune Teller room. Openning the vessel will release Merrick's spirit. While he will give no hints on locating the Jade Ixupi, he does show grief over what has happened in the museum.
Loose in the world
Given the vastness of the world, odds of encountering the Jade Ixupi would be rare. However, good hiding places for the Jade Ixupi might be any musuem with Jade relics in it, or any existing Jade status or jewelry. Given the existance of costume jewelry, it is unlikely to encounter the Jade Ixupi in jewelry. Most likely, the places to encounter the Jade Ixupi is in museums.