John Deere 12A

During the mid 20th century John Deere manufactured several models of hatchback size pull type combines for the small farmer. The John Deere 12A (pictured) was a popular and widespread model. I'd like to purchase a workable or restorable model. If you are reading this and know where one is, please drop me an email.
While a librarian can be buried under the literature relating to tractors (especially John Deere) the amount of information in print on the history of the combine in general and specifically these small machines is scant. I haven't been able to find any reference sources that detail the specifications of various models and makes of combine from the early 20th century on. For information, I've been relying on period material that I've found on Ebay. There is a need for a comprehensive reference source that covers all makes and models of combine from inception to the present day. Maybe if I acquire enough information, I will write my own.