Specsavers retail director Glenn Dunkerley said Austin had been coming into the store since he was a baby and he and others in the store had got to know the family really well.
"So we utilised our position in the public eye to raise a bit of cash for him."
Selling 50 pairs in the Bayfair store alone in August meant they had already raised at least $500 for his trip, he said.
The Tauranga Bridge Club recently donated $2885 to Austin's family while his primary, St Thomas More Catholic School, had raised $1785 from a bake sale.
Mrs Manning said the school's bake sales normally raised about $600 so was thrilled with the amount raised for Austin.
"One man walked straight up to Thomas [Austin's brother] and gave him $200 and said, 'This is for your brother'.
"It's just amazing. It's mind blowing. We can't believe how many wonderful people there are out there and how many people you don't know are so willing to get behind Austin and his cause."
The generosity had been surprising, she said.
Mrs Manning said when she started the journey she thought there would just be the odd donation through Austin's Givealittle page.
"I didn't expect the overwhelming support from our community. One of Austin's peers at his school donated $72 to his Givealittle page that he had been saving for a PlayStation and left a message 'I hope you have a good time when you are walking and I hope you like the feeling of it and nothing hurts'."
Austin also has picked up a penpal in Invercargill, also called Austin, through his Givealittle page, with the two writing frequently to each other, she said.