Hi the_intern,
I am not aware of a specific NI cable for the interdevice connector of the 4070. You should be able to use a four pin ribbon cable to connect the 4070 to the corresponding RTSI pins on another device. Also, the KnowledgeBase Article you posted actually shows which pins need to be connected.
Please post back if you have any questions!
Ryan D.
District Sales Manager for Boston & Northern New England
National Instruments