Amazon does have the Phiten Brand Necklaces and are fairly reasonable and look very nice. You can see them here: http://www.amazon.com/Phiten-Tornado-Twisted-Titanium-Necklace/dp/B00239DPEO
The one issue that I have heard about all the titanium tornado necklaces including the Phiten is the clasp design is weak.
This is one by Titanium sports which is equally as nice as the Phiten name brand: http://www.amazon.com/Titanium-Tornado-Baseball-Necklace-Black/dp/B005M99RDK/ref=pd_sim_hpc_1
The nice thing about buying through Amazon is they do have a good return policy. Personally I would say those made by Titanium Sports are equally as nice as the Phiten necklaces.