The Farnsworth lantern is still valid. We have one in our office and do several each month. You can also call the Regional Flight Surgeon's office. They have a Farnsworth lantern and will do it for you.
The Farnsworth lantern is no longer manufactured but there are some around the country.
See
http://www.myflightsurgeon.com/Farnsworth.html
The folks at
http://www.leftseat.com have a list of Farnsworth lantern owners but I think they charge you for the list.