"There were threats made, to the female as well. It was absolutely terrifying for them," Mr Pirihi said.
The male tourist was dragged from the van and punched in the face.
"The men then said 'right, you've got two minutes to decide what you're going to give us'. The couple went back to the vehicle, offered them $10, which is all they cash that they had on them at the time."
The offenders took the money but said it wasn't enough, so the couple gave them their clothes from the back of the van.
The men eventually drove off with two pairs of jeans and the man's empty wallet, which was later found discarded.
Mr Pirihi said police urgently wanted to speak to members of the public who knew anything about the attack.
"We suspect they [the offenders] were either living or working locally. I know there are shearing gangs in the area at the moment, so they may be connected to something like that."
Mr Pirihi said the couple flew home last night after three weeks in New Zealand.
"They'd had a fantastic time in New Zealand; they'd been down to the South Island and unfortunately this happened to them on their last night.
"They were very gracious and thankful for the support they received and said they still loved New Zealand and would have good memories [but] obviously they were very shaken by what happened."
The couple had provided descriptions of the two main offenders to police. One was Maori, of solid to fat build, about 175cm tall, with black hair and a goatee, wearing a black and white T-shirt.
The second offender was described as European, also of solid to fat build, about 178cm tall with short blond hair, wearing a green hooded sweatshirt with white writing on it and a green cap.