From my experience they are difficult in the states because many native species are endangered. I know the USDA National Plant Germplasm System tends to carry seeds like that, typically for research mostly. Might try them.

Does anyone have solicornia( marsh samphire, sea asparagus, pickleweed) seeds they would be willing to trade in the USA? I have been trying to get some and my orders from overseas were caught by customs and I cannot find a U.S. seller. I’m willing to pay or trade. I have over 100 varieties of tomatoes, and so many other veggie seeds and flower seeds too.

Looking for marsh samphire seeds (salicornia species)