Well I found a plain black stubby antenna on eBay, and I also purchased a 7" mast type antenna. The stubby antenna looked really nice but had horrible reception, so I returned it. The 7" looks much better than stock (which is about 13"), and the reception is pretty good too. It's slightly worse than stock, but much much better than the stubby antenna.
You can find it on eBay for about $6...
7" Roof Mast Whip Aerial Radio Antenna Universal for VW Honda Nissan Ford Etc | eBay
And one other note, I found out the 2013 and newer roadsters have a shorter antenna from the factory, about the same size as this aftermarket one. However, they also have a new base where it screws in. The 2013 factory antenna WILL NOT fit into 2010-2012 roadsters, the screw is too short.
Before:
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After:
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