New Zealand is believed to be the third country, following Australia and the United States, to formally ban them.
Brian Godfery, of Childsplay toy store in central Tauranga, said while customers had asked about them, he had never stocked them.
"I have never sold them because I was aware of the safety issues," he said.
Mark Rowley, of Boonen Electronics in Gate Pa, said the store sold earth magnets, but not as toys.
"They are so strong they have to put a metal bracket in the bag with them to stop them flying off the shelf," he said.
"If a kid swallowed them you could line him up against a metal car and he would stick to the car."
The ones sold by Boonen Electronics were not round balls, but shaped for use in electronic systems. The store did not stock the largest size - 50mm by 20mm - because they were strong enough to break bones.
"If you put one on either side of your arm they would stick together. If they snapped together on your finger they could break it," Mr Rowley said.
Mr Bridges said the magnets posed too great a risk to children.
"Because of their strength, older children have been known to use these magnets as mock jewellery, such as mouth or tongue studs. Young children swallow them out of natural curiosity," he said.
"In December a New Zealand toddler was admitted to Auckland's Starship Hospital after ingesting some of the magnets. Officials are aware of at least two other serious cases here involving hospitalisation and surgery."
