Hi All,
I just spent some time in Honolulu, and found that a bookstore/community center called Na Mea Hawai'i (
http://www.nameahawaii.com/) carries supplies for native Hawaiian crafts, as well as a number of good modern replicas of native Hawaiian weapons. One item they have is 20-30 yard bundles of sennit (coconut cordage) made in Yap. It's not cheap ($2.50/yard), but they're happy to ship it through the mail. If it's something you need for craft work, their recommendation is to phone or email the shop. This material isn't available in their online store, but as I found, there's a lot more in the physical store than online. If you're ever stuck in the tourist reservation that is Waikiki, they're nearby.
Cheers,
F