Normally swf.com doesn't like posting other places to buy things online. But, since they don't offer mangroves, they probably wont mind. If they do, mods feel free to edit this. I don't want to cause drama.
But, I know a guy who used to grow them under halides in his aquarium store in Greensboro, NC. He has a website,
www.marineecosystems.com. Check it out. If not, look up marine ecosystems in Greensboro NC and give him a call. Maybe try a couple of places in Fla. too. Good luck.