Chuck and Jim,
There are other "off the shelf" brackets that can be mounted inside the mirror housing. I have done this a couple of times. You may need to drill a couple of mounting holes in the pot metal.
When finished and the back mirror cover is back on, no one can tell the difference.
There are also brackets that mount on the top mirror arm. The CB cable inside the mirror is long enough to reach above the mirror to the new outside bracket if you stretch it out.
onezman
http://onezman.tripod.com/whitehotrvhauler