Both your debit card company and eBay should be able to help. For future, PayPal is a great way to go because they have six months of buyer protection. As long as you don’t use their friends and family. Just use the standard goods and services.
First thing though contact the seller and tell them you goo got opinions that it’s not real. Send them a link to this discussion if he raises a fuss. He’ll probably Pooh Pooh it but it’s probably enough for eBay if you have to go there.
Real ones certified by the top three authenticators typically list at over $1000. You can negotiate usually, but you’re not gonna find a real one unless you get exceptionally lucky for a lot less.