My local Nissan dealer occasionally has collared polo-style shirts with Nissan or Nismo logos in stock. I looked through their catalogue recently, but I don't remember if they had any shirts specifically referencing the Z. I had them order me some Z hats.
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2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed | |