Lost Nikon Travelite ex eye piece

I'm supposing by eyepiece you mean the rubber or plastic eyecup. The eyepiece is the whole unit that contains the lens. Nikon has a service center in many countries. If you have one in your country then they can order the part. I have ordered from Nikon. They find the part number if you tell them your model and can email you an order form. Alternately Binoculars.com is very good to deal with as is Adorama Camera in New York. Both will sell internationally.