I am still snooping around for seed sources, but here is another possibility:
Pandanus tectorius.
P. tectorius is another great choice for larger riparium setups. It grows very well in riparium planters in freshwater or lightly brackish water. It can handle a certain amount of salt because it grows on the beach in Hawaii and elsewhere in the Pacific.
As it grows
P. tectorius develops these awesome stilt roots...
