I use a Cobra "thru-the glass" antenna.  I have it mounted on the upper
right of my windshield.  It is not the best range wise, but it was
affordable $25 and serves my purpose (talking while caravaning).  It looks
and attaches just like a cellular phone antenna.  I have it attached to a
$30 Uniden 40-channel radio.
    Not the best equipment in the world, but has summoned help and provided
many hours of conversation on road trips.

Jason M. Yasment
'84 Westfalia (up for new trans and brakes)
'98 Jetta TDI (in the shop with US$3600 worth of rear end damage)
'98 Ford Escort (rental car)