The seller can refund a Paypal payment with a few clicks. He could have done this when he told you he was out of stock.
Do NOT wait for a 'replacement'. It won't arrive either.
If he is putting you off about refunding, go to the Resolution Centre at the bottom of this page and open an Item Not Received dispute.
You have already communicated with the seller, so skip that step.
If the seller cannot show Delivery you will be refunded. If he doesn't do it, eBay will and then go after him for their money.