If you want to do it yourself, I'll tell you how I did mine. I honestly believe that I was one of the first people to have a short antenna for my Mustang. Story: I was haulin' ass down a Highway that is straight away's for miles and out of nowhere, a bird flew across in front of me. My antenna hit the bird, cut it in half and I had two parts of bird on my windshield and a crack from the 60 foot tall stock antenna. I was like "I'm going to make a short antenna somehow" (This was a few years ago).
So I went to lowes, got a few ceiling fan bearings (round with a hole already in the bottom) and cut my antenna, sanded it down, epoxy glued the bearing on the top and painted it. I show a friend of mine (also had a Mustang) and like 2 days later I saw it on Mustangworld under the "How To" section (althrough they didn't use the bearing for the top).
Rant over ... That's how I made mine so if you want to be cheap and different, there you go. I hate seing shorty antennas being sold although the aluminum ones are tight.
Yeah last winter when I put mine away for storage I took the antenna off and snipped it about 8" down. Superglued it back on and painted it, looks great!