I have not seen any good deals on plants from the usual vendors. Usually, if you say what you are looking for and post it in trading areas of boards like this, someone will pop up with what you are wanting. Also, ebay has some on occasion.
California and Texas have laws against importing "invasive species" of marine plants. None-the-less, I live in Texas, and still have had shaving brush shipped to me, although the site says that they cannot.