Despite a crackdown on Kiwi gang merchandise, eBay is currently selling Mongrel Mob and Bandidos MC knock-offs.
Kiwis have previously been warned not to buy knock-off clothing over safety concerns.
But American-based eBay is selling ready-made knock-off Mob T-shirts for as little as $23 in both black and red.
The words "Mighty Mongrel Mob Aotearoa" have been printed on the shirts along with the gang's emblem.
The seller, from Indonesia, has been advertising the knock-off items since December 18, along with a variety of other knock-off t-shirts.
Another Indonesian-based eBay user is also selling knock-off shirts from gang Bandidos MC, who entered New Zealand in 2012.
The gang's logos are printed on a black along with the slogan "All men are created equal, only a few become Bandidos".
Follow rip-off sales last year, members of the Mob and gang academics warned the public not to buy knock-off products that were being sold overseas.
They warned trouble could brew on New Zealand streets if people are seen sporting the rip-off product.
Life member Harry Tam has said there could be serious consequences for those who are caught wearing the knock-off products.
"Obviously this has never happened before but I'm sure if people do it, they'll no doubt find out in due course what the consequences are," he told media outlets.
"When it comes down to it, the people purchasing these are putting themselves in jeopardy.
"There's certainly no mana behind the [counterfeit] patches.
"All I can say to them is don't wear it. If you own one, send it back to them to ask for your money back. It's probably not a good idea to be seen with it, with something that doesn't belong to them."
Police also warned members of the public of the potential dangers of wearing the knock-off patches, saying they risk angering the gang as well as associating themselves with that kind of activity.
"Police constantly monitor the gang situation in New Zealand, and while it is not illegal to wear, buy or sell gang insignia, police would remind those who choose to wear it of their obligations under the relevant legislation and bylaws," a police spokesperson said in a statement.
The Mongrel Mob was founded in Hawke's Bay in the 1960s and has long had chapters not only in New Zealand, but also Australia.