Reminds me of Bender from Futurama:

 

my thought was.... stealth?? cosmetically pleasing??



clearly those words don't mean the same thing to different people...

 

you could check out a marine antenna--(designed specifically for a boat) a fiberglass boat won't have the metal a car does to use as a "ground plane" and works well without one.
My boat came with an antenna that has a normal cable connected to the radio and on the other end, instead of a metal antenna, it ends with a thin wire about 3 feet long that's just run along under the front seats--reception is OK but I have nothng to really compare it too. The antennas are really cheap (under $10) from boat supply stores like www.westmarine.com If you used this type you may still want to put it inside the bumper to get it outside the metal body of the car.
good luck!

 

here's the link to the antennas I was talking about. In addition to the long wire one (at $9) . there is an anplified one that's about $16

http://www.westmarine.com/webapp/wcs/store.../man/asc/0/grid

 

NICE find, jetboater! Thanks! That might just be the ticket.

 

Glad to help.
If I remember correctly, the OEM antenna cable from the radio ends with a connector that plugs into the orginal antenna amplifier inside the rear fender that the rubber antenna mounts to--I think you can just unplug it and plug in the cable from the new antenna and run it where ever you want. If you can get up behind the bumper, you may want to consider getting the one with the built in amp for $16 and mount the entire antenna back there under the bumper--it should be waterproof since it's made for a boat and it would get you better reception than the plain thin wire one
good luck!