I have access to seeds but since you're in the USA and I'm in Canada sending them is a little more complicated because of import controls. I'm sure someone in the US will be able to help you. It's a lovely tree in flower, but seedlings pop up all over the place around here. Have you considered that it is reportedly toxic to cattle?
" The seeds, bark, and leaves contain toxic proteins that have caused sickness and death in cattle, horses, poultry, sheep, and humans. The plant should be considered toxic to all animals if ingested. Children were poisoned (with rare reports of fatalities) after chewing on plant material, especially the bark. This tree can be found around older farms and houses and is also planted along fencerows. Children should be taught not to ingest any parts of the plant. If older trees are cut down in areas where livestock have access, make sure that the animals do not ingest any sprout (sucker) growth that may emerge from the stump (Hansen 1924, Kingsbury 1964, Cooper and Johnson 1984)."
However: "In a North Carolina effort, browsing by a combination of
cattle and domestic goats effectively controlled the height
growth of black locust. After 4 seasons, all black locust were
dead. Since black locust can be toxic to cattle, caution is
advised. Black locust is raised specifically to feed domestic
goats in Pakistan and New Zealand, and they appear to be a
better choice for control."