try here:
30-1/2" Replacement Telescoping Antenna - RadioShack.com
if you want a different type try typing "replacement telescopic antenna" or "telescopic antenna" into a google image search,you'll find hundreds of different types and lengths.
google is a fantastic tool if your very specific what your searching for.avoid words like and,the,or,etc when searching as it will throw up thousands of hits with those words.if you type in a telescopic antenna,most hits will include the word a,
if you type in only telescopic antenna then all the hits will be sites with telescopic or antenna in them,
to be even more specific type "telescopic antenna",that way the inverted comas tell google only to look for sites with both telescopic and antenna in them,thus narrowing down your search results and also the amount of bullshit you need to wade through to find stuff.
learn how google works and you'll find your way around the www much faster and with much more success.a good start to learning google's secrets:
Google search basics : Basic search help - Web Search Help
more advanced stuff here:
Google Search Tips 2005
although just typing google search tips or google search hints will find thousands of tips.
Where to buy these radials? 
Linear Mode
