If the buyer is helpful ask him to agree to a Mutual Cancellation.
Then send him the request.
When he agrees, eBay will free both of you from the transaction, you will get your fees back and both of you can leave feedback.
Now this also means that a non-too-ethical customer may decide that he is allowed to keep the item that you have refunded him on. So add to your request that he return the refund WHEN the item arrives using Paypal's Send Money service.
He probably will since most people are honest and since you have told him how to do it.
Because you are past the 45 day point, this may not be possible, but eBay has extended the Dispute deadline to 180 days in some circumstances, so it is worth trying.
