Yaesu wants an outrageous price,(abt. $70.00), for their separation kit for the FT-7100m. With all the problems of the radio, they should give the kit away as a peace offering, but, that is another story.
The interface cable for the radio and head is nothing more than a 6-conductor cable with a RJ-12 modular plug on each end. Walmart sells 6-conductor telephone cables by Southwestern Bell. These cables must be modified to work with the 7100. Cut the plug off one end and replace it with a new plug. Be sure and rotate the plug 180° from the one that you cut off. Crimp the new plug and you are set.
That''s all there is to the project.
If you have a crimp tool, the cost for the project goes way down.