The issue has been discussed many times. Three options was available.
1. Shark Attack Antenna
2. Guppy Attack
3. S2000 Antenna
You can still buy the first on amazon (Metra 44-UA46), the second one has been discontinued and your best bet is from other owners, not sure about the third one as this one required drilling on the fender to fix the unit.
In fact, the reception really depends on where you locate. I live in metro and my shark attack antenna works just like my OEM fish pole. If you live in rural or mountain area, I suggest you keep the fish pole.
Try to use search function get to more information about nsx antenna.