Very likely it has not made it across the pond. Where did you read about it? Conifer Encyclopedia or Henk's Garden? I have found many cultivars of Tsuga diversifolia that sound very interesting, but it seems most of these are only in Europe.

Maybe Edwin or Henk could provide you further information about that cultivar.

I'm not familiar yet with info about it or with a source from were you can obtain this cultivar.
Henk's stockplant died and the one at the pic in the new RHS Conifer Encyclopedia was taken at the Kohout Nursery in Germany.
Unfortunately he doesn't mention this cultivar at his stocklist...