At http://www.acecomponents.com/ their inventory lists 100 BU406 in stock. Of course, this just might be the date code marked on some one leaded interdigitated phramisoidal confobulators that are misfiled, so you might want to have a human being break open the tube and see if there is a physical resemblance. Many years ago the printed ACE catalog listed the BU406 at $1 each. Good luck [8D]