Saw cables like this on Amazon. There are some which takes usb power like the 2nd link. HDMI to RCA Cable, HDMI to RCA Converte,1080P 5ft/1.5m HDMI Male to 3-RCA Video Audio AV Cable Connector ...

Anyone searching for a HDMI to RCA Audio and NTSC or PAL Video Adapter will be pleased to know that one such device has now arrived at the Adafruit online store and is available to purchase priced ...

In reviewing many product pages, I found a single ~$70 HDMI switch w/ RCA audio out that *claimed* to do what I wanted but was from a no-name brand on a no-name website; this was sketchy enough ...