Icelandic sheep, Cashmere goat, and Yak streamer hair are the only ones i could find in a search that were close in product description. But most said they were 5"-8" length so only the few longest fiber would be that length. Spirit River has a product called SeaHair that is a kinked nylon.... but not too kinky.
Above was mentioned horse hair and synthetic hair extensions and they may be your best option.
Are you trying to create a specific pattern, style or look? Maybe there are other materials that you could swap - rabbit or squirrel zonkers come to mind since you can cut them to desired length - and they come in a Magnum size if you need a more full look. There are some very long saddle hackle that could be used but that would eat up some $$$ to get a full look.