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There are hundreds of species of Aroids in S. America, probably the majority of them epiphytes (Anthurium, Philodendron, Monstera spp. would be examples), and I would think that some of them must grow in similar situations to Anubias and Bucephalandra species.
You could try the <"International Aroid Society"> to find out if any of them are commercially available (my suspicion would be that they aren't).