Here is the response I received when I opened a ticket earlier this year.
On Tue, May 26, 2015 at 2:11 PM, Obihai Support Team <support@obihai.com> wrote:
Hi Dan,
At this time, the EHS cable is not available for sale yet. It is expected
to be available later in Q4, 2015.
Thank you, - OBi Support
For Christmas I hope to receive an EHS cable. I would also accept a wiring diagram and build my own as a short term solution.