Kauai Nursury and Landscaping has had named varieties in the past. When I drove by there last month they had a banner saying they would ship to mainland locations. I already had a few and was getting some more from a local friend so chose not to investigate further.

Coming from Lihue its on the opposite side and past Kauai Community College on Highway 50. They actually have quite a few Plumerias along the roadside as well which put out a nice show. Good luck and let us know what you find.