I have to agree with Mary, Seattle area LFS have some great plants if you know where to look. Occasionally A Place for Pets in Burien has Java Fern 'Trident' and Pogostemon erectus. At Sierra Fish and Pets in Renton they regularly have Nymphoides sp 'Taiwan' and occasionally they have Hygrophila pinnatifida.
Robert may have to make a trip up to Seattle and do some scouting; the selection of aquatic plants in Seattle has changed substantially in the last few years!
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Greater Seattle Aquarium Society (GSAS)