you can try the Ferrari showroom (not an actual dealership) on Park avenue and 50th or so.. i don't remember the actual cross-street, but it's in that vicinity. prices will be at full retail though. last i went by, they had some decent stuff.. challenge stradale hats/shirts, enzo keys (cut, of course), model cars, etc.
The store in Milan by the large church or the one across from the factory in Maranello. It'll give you a good excuse to travel to Italy
I was at that factory in May & spent 3 days in & around Modena & Maranello. Be sure to go to the Galleria Ferrari & the many model car shops in Maranello. Also, remember - no cameas inside the factory. One guy who was there when I was slipped a small camera into the factory & got caught taking photos. It was not a plesant experience & I'm sure he will never be allowed back. The trip will be a memory you'll have forever. Enjoy!