mteal is right, the houseman book will be your best choice. it's available through interlibrary loan at your local pubic library.
i've seen pictures of it in a huge book about the greatest american plays ever staged, don't recal exact title, but greatest, and american plays is in the title.
frank brady's book is a very reliable source.
and look in the library of congress for the wpa. they have the scripts that were sent to the theaters. it wasn't that welles decided to do macbeth, then decided to change the setting, the wpa has like a supply of scripts and it seems they had to pick from that stack. and it was his first wife's idea to stage it in haiti.
but your best bet would be the houseman book. it's a great book. before i had a copy machine and could pirate at home in my spare time, i stood at a 7-11 copy machine at 3:00am, and while the store-hadji slept, i pirated all 600 pages. it was well worth it.