Here's how I did mine. Two 'L' brackets from Home Depot and a couple of wood and metal screws.
BTW, the Epia has a line input you can run audio into. Many people play their XM or Sirius through it. Also, several touchscreens have aux video in ports that will switch to that input automatically if they sense a signal on the line. If you power your camera when your backup lights go on, you can automatically switch the inputs.