I very much doubt that eBay or Paypal will help you.
Both had a 45 day deadline on disputes and refunds until recently.
Your second avenue would be your credit card, which you really paid with. Again, while cards do have longer deadlines, they still have them, so while you should phone the 1-800 number and ask the rep about a chargeback.
Again, I have my doubts, but if you don't ask they can't agree.
If your seller is in North America, you could try going to Small Claims Court. The one in his jurisdiction would be the most useful. And now you are adding to the (very reasonable) cost of the Claim the further costs of getting to the Court along with hotel and food bills.
After school is out, we still learn life lessons.
This has been one of them.
Don't allow too much time to pass before moving to a refund.
Generally, that time would be 30 to 40 days, not several months.