“Raised the compliant with ebay and they have "Made the final decision" and refused my refund”
The case goes to seller in the first place, not ebay. Unless you follow correct procedure you will always lose.
What exactly did you do? You should have opened a “not received case”. If no response from seller within 3 days, then you escalate to ebay who should refund.
Now you will have to try your payment provider.