FWIW, I purchased one of the GPS antennas from E-Bay.  If you search old messages the posts, and my report on performance, should be relatively easy to find.  For the most part I haven't needed the antenna but figured for as cheap as I got it, I couldn't pass it up.  
If you shop elsewhere for the antenna, the connector on the iFly is (I believe) a MCX connector.  It's nearly the size of the connector for my Lowrance GPS's but misses by "that" much.