Saw this at Amazon:

 

pi tie blue.png

And naturally had to buy it for $20 USD, though now the price has climbed to $25 USD.

 

It's microfiber instead of silk.  A little disappointed its only 58 inches (1.47 m) long, as I am 6'1" or 73 inches tall (1.85 m), and prefer a longer tie around 67 inches (1.70 m).  This was just barely enough tie for me, so anyone much taller than me should probably not get this.

 

Still for the sheer novelty of the PI Geek that I am, it was totally worth it.

 

To find other outlets, you may try a browser search on: blue microfiber pi tie