JEB & Oscar...
Flax is more or less a cultivated crop. It is not a plant that I harvest locally unless I plant it myself. That being said, I'm sure one could purchase flax in any form (seed - fiber) on the Internet if you were so inclined.
The process that I demonstrated is fairly universal to many different natural fibers. Locally, I can find nettle that grows between 3'-6' and it yields some of the best natural cordage strings I know of. However, this year was a dry year and it did not grow well so I use the flax that I had stored in the rafters.
Scott