I have gone down this route before. You want to get a name and address, then send out messages to those on his feedback profile, who have personally sold something to the seller. You heard me right. I am sure your seller has purchased something on eBay in the past. You contact the seller and explain your situation to them and ask for an address. The address is always shown in Pay Pal. I have done this twice on two different individuals and have been successful at obtainning an address. Another route is to purchase another item from the seller (something of small value) and do it from a different eBay account and then when he/she sends you the item, you should have the return address label on the package.
You could also contact another recent buyer and see if they still have the original packaging...which is a long shot, but it might work. Just be really sincere and don't get long in your explanation. Above all else, leave a negative feedback on the seller's profile!
And above all of this, open up a dispute on eBay for item not as described. eBay has a 100% full guarantee + original shipping paid...AND they will pay to have you ship the item back. But I am guessing that this happened longer then 45 days ago. I believe eBay only allows 45 days to open up a dispute.
Hope this helps. Good luck to you.