It's not the first time this year that the royal couple have supported Make Give Live.
On New Year's day they shared a photo of baby Archie wearing a Make Give Live Cocobear hat in Canada with their 10 million followers, which Conza says inspired thousands of orders from around the world.
"Demand for the hats have continued throughout the year and the sales have created an opportunity to support even more Kiwis through a tough 2020," says Conza.
"I recently posted a message on social media asking how we could get a card to them sharing how grateful we were to Harry and Meghan for shining a light on the work we do."
"This year we have donated over 3500 hats to people in need."
She did send a Christmas card to the Sussex family but the letter from the Duke and Duchess suggests Prime Minister Jacinda Ardern may have played a part in ensuring the message got to the couple.
"It said Jacinda Ardern had let them know we were trying to get in touch and that Archie continues to wear our beanies as they have one in every size."
