Must be a good reason why they're not, though Lin. We speculated up above as to why it would be unavailable, and a couple of answers were that it was disease prone, or that the variegation proved to be unstable i.e. it reverted to plain green too readily.
The fact that
@gopher1964 found that one big specimen at a nursery is encouraging, though. I wonder if they re-start the plant at intervals to maintain its health and/or appearance.
Please take pictures to post if you go back, gopher?