I was also wondering about this. I thought it be a great plant to add to a refugium so it would look like a sea grass and sand bed like what I've seen in the bahamas. None of the big online/mail order companies sell it. I wonder why?
I am trying to get my act together on having a seagrass refugium, and have been doing a little hunting. Two places that carry them are: Florida Pets Inland Aquatics