I dont think you can send him a return label through ebay unless he opens a return. I have been here myself. You can purchase a label on Pirate Ship etc and just email a copy of the label.
I did this twice! I mixed up two packages and send the 2 buyers the others item. First time I asked them both to open returns, sent them the labels and got the items back. One buyer cancelled and the other waited for their item, delayed for sure.
A couple months ago, I did it again, because the first time wasn't enough. These were both inexpensive items so I offered each buyer a full refund on their item if they would accept a 'return' label addressed to the other buyer and ship the item to them. It worked out well, both buyers were awesome. But, these labels I purchased on Pirate ship and emailed them the PDF copy of the label.
While I am confessing, just this week, yes 2 days ago I send the buyer the wrong item. He purchased an inexpensive hair clippers from me. I had a few for sale and when I packed his order, I accidentally sent him one that was 4 times the cost of the one he ordered. As you probably guessed the buyer was fine with the error and gladly accepted his new clippers.
Good luck. Don't sweat the small stuff
