Here is why the info is so hard to find:

"We cannot provide the internal cable schematics, but the AT89ISP cable is available for order now. ATMEL part number is AT89ISP and It is a low-cost item. Please contact your nearest ATMEL sales office or distributor for the price.

To find your nearest ATMEL contact, you can use this link:
http://www.atmel.com/contacts

Regards,

Atmel 8051 Microcontroller Apps
USA"