Police said the item was found in the vicinity of the Whangaehu River mouth, south of Whanganui.
The search is focused on thecoastline between Pātea and Peka Peka.
The diver was reported missing from a ship shortly after 1.30pm on Sunday.
Police said the missing man’s family had passed on gratitude for the support of their community and for all of the people who have dedicated their time towards the search over the past week.
Police would like to hear from anyone who finds items on the coast between Pātea and Peka Peka that might be relevant to the search for the missing diver.