I have the following magazines and advertisements that feature Nelson Eddy.  I will try and update this list when more things
become available.  Hope there is something you can use!

Life 9-27-37.  Nelson Eddy on the cover dressed in a marching uniform holding a baton.  $34.95

Adverstisements:

Life 11-24-41   
Life 10-21-46
Look 12-2-41 color movie ad
Life 1-26-42 Columbia records ad
Life 2-8-37 Maytime ad in color
Life 1-31-44 movie ad

Articles:

Life 1-24-38