18 or 20 inch in length, approximately 6mm in diameter, 14K or 18K
yellow gold womens necklace or chain in a bamboo motif.

Here's one for $1,780 but no mm size is listed:
http://www.ice.com/customer/product_detail.jsp?product=55694960&sourceID=dealtm_03

No luck with yellow gold exclusively (lots of silver out there) but
here are some two-tone 14K:

http://www.widgets.ws/prod/GoldenMinecom/2077/Bamboo-CZ-Necklace-17-inches-194-grams.html

http://www.widgets.ws/prod/GoldenMinecom/2077/Bamboo-Necklace-17-inches-227-grams.html

http://www.goldenmine.com/productlinkcloseup.asp?site=link&pagenum=1&imageurl=F2004&AID=10275564&PID=678364

A cached page at http://216.239.39.104/search?q=cache:bQyfRXkt_w8J:www.jewelrydistrictinc.com/+6mm+%22bamboo+bracelet%22&hl=en&ie=UTF-8
showed one that led to a Paypal purchase page but I don't know if they
are still available as the image on the page was missing.

If no Researcher is able to find one exactly as you describe, you
might consider purchasing three of the gold bamboo bracelets like the
one shown at http://graciousrose.com/bamboo_bracelet.html and hiring a
jeweler to attach them to form the necklace you seek.  Or inquire at
an established jeweler's if one may be custom made by ordering the
chain-by-the-foot from the manufacturer and the jeweler adding the
clasp and bail to the specialty chain to complete a necklace.  The
latter is probably less expensive than the three bracelets.

Best regards,
journalist-ga

call those guys: www.levor.it
rgds