On a related not, I really appreciate you including the common names. I don't know scientific names and it is a pet peeve when those who do, use them without including common names. I have neither the time nor desire to learn the scientific names and find that they just get in the way of a good conversation. I am not saying this about you but many people use the scientific names just to show off their knowledge.
I've ordered sea buckthorn from Saint Lawrence nurseries in New York. Not exactly a regional source but their stock was good quality and survivability after one year was about 85%. The year before I got six Leikora variety from some outfit in Oregon and survival was 5/6. Last year most grew well.
Lawyer Nursery out of Plains, MT lists a "wild" sea buckthorn but you have to buy in bulk. Same is true of autumn olive (Eleagnus umbellatum). I got 25 autumn olives from Lawyer last year and the survival was 24/25. Most thrived. Lawyer's stock, at least the things I ordered, was very good.
As for goumi, I have nary a clue on a PNW source. Jung nursery out of Wisconsin lists it in this year's catalog. I've always hesitated to try it as the sources seem to vary widely as to its survivability in zone 4 (even though we've not had a zone 4 winter temp in the three winters I've lived here.) Jung lists their goumi as suitable in zones 4-8.
Have you tried Burnt Ridge in OR or Raintree out of WA? They both have extensive listing of plants. Good luck.
You are most welcome. Have you looked into JL Hudson seeds as a source for some/all of your plant needs? They have an extensive catalog of seeds and could likely help you fill out your planting needs. Check 'em out.