This remembers me of a friend wanting to buy an used TV for pennies, and demanding a two-year warranty for it.
The only way you have to relief you ancestral, human fear of being scammed is buying a brand new card - if you find one.
On the other hand, thinking that every used board on ebay is being sold because it was defective and has been processed with 11 minutes in the oven, well... it doesn't really work like that.
Having bought plenty of used stuff, I have been seldom disappointed. Keep in mind that you get what you pay for. Original package is missing, sometimes the board is sent in a box without protection at all, sometimes it' a DOA. You can ask for a refund or another item to be sent; in general, buyers are supposed to be right - I am a lot more worried when I sell something!
Of course, if you still like the idea of a piece of paper that screams "warranty", you can bring the whole thing to an authorized repair store.