Once it is refunded, why would you want to return it on your dime? The transaction is now closed and the seller doesn't want it, otherwise they would have had to pay for the return.

The correct method would  have been to open a dispute for Item Not as Described. This would have achieved the same outcome, but in a formal manner that Ebay can track. In the dispute the seller would either have had to send a return label (if domestic), postage funds (if overseas), or refund you.

Please read up on what to do when things go wrong. You were lucky you got a refund at all, since most sellers will not act unless there is a formal case opened.

Just chuck the item away or sell it yourself.