Hi,
I can't say that I've seen any good permanent antennas.. But I really haven't had any problems with either my XM or Sirius magnetic antennas that came with my players. The Sirius one (which I'm currently using) is giving a better signal though. The connectors for my XM and Sirius players are the same, so I was able to swap the antennas.
If you are adventurous, you may want to see what the connector on the Nitro's factory satellite antenna looks like (after market option.. don't know if they sell just the antenna though). I have seen this picture posted that shows the connectors, but unfortunately the angle is off, so you can't really see the exact shape. If that fits, you could use that, that would definately give the 'cleanest' look.. Or then again, maybe someone else already has and may be able to better answer this question.
Here's the pic of the connectors:
I couldn't find any pics of the factory satellite antenna, but someone probably has one on here.. Hopefully I helped a little.
