There was a party in Europe that sold an HDMI cable with adapters for the Head and Radio ends which I purchased.  It was sold on eBay.  It worked.  I do not know if it would still be available.  I extended the HDMI connection a bit too far though, (20'), and experienced sync buz in my transmit audio coming from the video signal.  I overcame this by using CAT5 cable for the micraphone and running it directly to the RJ45 jack on the radio.  I don't if this will be of any help to you.  My transceiver and amplifier reside in the "trunk" of my Honda Ridgeline and works well!