I haven't seen sea buckthorn in the Missouri tree sales in the last few years (and I watch those closely) I do have some of the seeds from Jiovi, but due to weird stuff, haven't planted them yet. I'm in Southern Missouri, and looking forward to seeing if they make it. everything I saw said give them seriously full sun, so they are going along the south road here, to be a windbreak and a good thorny hedge with southern exposure. Jiovi might
sell you cuttings too, worth asking, nice folks :)
Edit: They need cold stratification to sprout, did you do that?