This won't help you but most of the nurseries around here (NC) grow it from seed collected at the beach - at least the ones that I know well or have worked at do. Its pretty common and easy to grow.

Everyone I talk to says it is very easy to grow and very common on the east coast. Nearly impossible to find elsewhere, though!

Thanks John!

I will add that in my experience it doesn't bloom long as a single plant - maybe two weeks. It is striking while in bloom though. When at the coast there are clusters of plants at different sizes so they appear to bloom for months. You can find solid white ones as well as the normal pink. I'll ask around our seed swap group to see if anyone has any seed left over from last summer.