I asked E. J. Fischer where he got the originals for his propaganda posters. His reply:

There are a ton of poster archives on the web that you can find using Google. Northwestern University has a really good and fully searchable one, located at: http://www.library.northwestern.edu/govpub/collections/wwii-posters/

The Old Eagle poster archive has some good international posters: http://www.oldeagle.nu/post/

A Google search for "propaganda war posters" should have several more as well.

Go forth and multiply.