You know, when you supply the merchant's name or location, it's helpful to supply the zone, too. Jaren Cloudchaser carries these. He's in PoK, location -94, 1474, -108.
There is another supplier of the arrow shaft molds. Livam T'Lant (located in the Jaggedpine Treefolk building) in Surefall Glade -115 x -280. Great spot for all you Karana fletchers.
So far I've found the best sources of information for tradeskilling to be found on EQTraders.com, though the best fletching info on EQRangers.com - follow the link along the left hand side for Trades & Training Guides. You can also follow the links above, next to Recipes.