Go to the listing in your Purchases list.
Click on Contact Seller.
It's there somewhere, keep looking.
Don't try to do this on a mobile device, use a desktop or laptop.
If you don't own one, try at the public library.
You can send the seller an eBay Message there.
If that doesn't work, you can call eBay for his contact information. Note that he gets yours at the same time.
Bonne chance avec!