FWIW, I've been watching for red backs for a couple of years now. They haven't shown up on any stock lists and when I spoke with Kevin K. about them at Reefstock, he hadn't seen any either. He did say that if they became available, he would pick them up for DD, but again, they just aren't being brought in. They aren't rare in their environment, as mentioned previously.
A good friend of mine bought a lovely little Asfur about the same time I got my baby Mac, 12 years ago. The Asfur has grown to about 5.5" and stopped, while the little mac went from 1.5" to 14" during the same period. Stunning growth over a 10 year period.
-Rob