I bought these memory cards on Ebay, from a seller in Italy. Still sealed. As far as I can tell, they look quite original! I hope they will work without problems. :
8MB Memory Card - Playstation 2 – Retro Raven Games
8/32/12mb Megabyte Memory Card Game Memory Card For Sony Ps2 Playstation 2 Slim Game Data - Memory Cards - AliExpress
Amazon.com: PlayStation 2 8MB Memory Card (Black) : Video Games
SD8MB Panasonic 8MB SD memory card
PlayStation 2 Official Sony 8mb Memory card - Black - USED available at Videogamesnewyork, NY
Sony PlayStation 2 8MB Memory Card Genuine/Official/OEM - Red • Access – Mikes Game Shop
8MB Ps2 Memory Card-Yellow - D&J Computers And Games
Lot of (9) Memory Cards Playstation 2 Sony 8MB Game Cube Max Memory 16MB PS1 | eBay
8MB Ps2 Memory Card-Blue - D&J Computers And Games
Amazon.com: PlayStation 2-only memory card (8MB) Ceramic White : Video Games