Sorry to be blunt, but sell it elsewhere ! Without an EAN or UPC you won't be able to list it correctly on Amazon. Also, 'work arounds' are NOT the best idea on Amazon. All just IMO. When you say 'purchased from the vendor', what exactly do you mean ? - from the company ?

As you say this is your first item, you need to read thoroughly Amazon's Seller University - tells you all you need to know about selling on Amazon. Presumably this is a new seller account ? - and hopefully you opened a BUSINESS Seller Account - which is what you need to sell goods for profit, and are you registered with HMRC as self-employed (possibly sole-trader) ?

Selling on Amazon is not just about buying some goods and then selling them on - there is a lot more to it.