I grabbed a copy of a free (!) publication from the Cryptologic Museum
entitled "The start of the Digital Revolution: SIGSALY - Secure Digital
Voice Communications in World War II". It mentions that you can visit the
library and look at "The Green Hornet... America's Unbreakable Code for
Secret Telephony" -- privately published in 1999 by D. E. Mitchell. It
says it is very complete.
And yes, the museum only has a mock up. But when you consider the noise
disks, it's an amazing feat.