EBay only gives about 45 days for Item Not Received Disputes.
Instead go to your Paypal account. Their Resolution Centre in on the left side of the page.
You have only 180 days.
If the seller cannot prove delivery, PP will force him to refund. If he doesn't do so willingly and promptly, PP will refund you and go after him for their money.
Hard.
If PP turns you down for some reason, go to the credit card you use to back your PP account and ask about a chargeback. But PP should be all you need. (Still a good idea to back you PP with a cc and not your bank account or a running balance.)