The Royal British Legion has appealed to eBay sellers to consider the charity after an official £9.99 poppy sold for £175 on the auction site.
The gold-plated Buckley Poppy Brooch, inlaid with Swarovski crystal, has sold out on the RBL's website but at least 20 were attracting bids on eBay on Wednesday.
One sold on the auction site on Tuesday night for £175, while the next one due to sell later on Wednesday had attracted a £62 bid by mid-morning.
Some carried an accompanying note claiming that 10% of the winning bid would be donated to the RBL.
Tuesday night's seller did not respond to emails.
A note on the RBL's Poppy Shop web page advertising the brooch reads: "Due to the overwhelming popularity of this item we are not able to guarantee delivery before remembrance on any new orders placed."
The RBL appealed to sellers to make a donation to the charity.
A spokeswoman said: "We obviously cannot stop people doing it, but we hope everyone who does sell a poppy on an online auction site makes a donation to the Royal British Legion."
The RBL provides welfare services and campaigns on issues affecting service people.
It raises funds through the annual Poppy Appeal.