"We got back in the campervan and didn't even realise our bags were gone because there were no signs of forced entry so we drove up to Kiwi North and couldn't find the bags," Mr Sheldon said.
Earlier last week, another campervan they hired broke down between Coromandel and Auckland and since then, they decided to put their personal items in the bags.
Their emergency travel documents were due to be ready before both flew out to Australia on Monday. Other lost items were insured.
Both tourists, who are friends from London, had initially planned to visit Cape Reinga but the thieving incident has put them off from going that far.
Instead, they intend to spend a couple of days in the Bay of Islands before returning to Auckland.
Anyone with information on the theft can contact Whangarei police on (09) 4304500 or email Mr Sheldon on willsheldon@hotmail.co.uk or Ms Boanas-Evans on iboanasevans@gmail.com.