There are disguised antennas used in the land mobile service that look like
AM/FM mobile antennas. (they're intended for undercover police work).
Try 
http://www.sti-co.com/index.php
Another, simpler, solution that you might get past the XYL is a 'cell look-alike'
antenna. There a number of manufacturers that produce those.
Steve
 I'm wanting to keep peace within the family.. NO!  Extra antennas on the
 vehicle..
  I want to install a dual band 2m/440 mobile using the AM/FM antenna that is
 on the vehicle..  It will be mostly used for receive, BUT....
  Other than a duplexer and tuner (s) What is needed to STOP the RF from
 damaging the AM/FM radio in case I want to transmit?...
  Any help on this??