ORA breeds them; I hear the yellows are easier than the blues from a breeding perspective. I tried to purchase ORA fish for my assessor harem, but couldn't get more than one fish from them
I gather that shipments from Australia come in about every 6 months and that's it. As I was looking, an LA wholesaler just happened to get a batch. The LFS owner that was trying to get them from ORA for me called me from the wholesaler. I picked them up still in the bag when she got back to the shop, and took them home.
It was a troublesome QT -- they were in fairly good shape but it certainly was a long, stressful trip. They had several illnesses plus worms; all treatable but hampered by fighting. 4 assessors in a 12g QT was NOT a good idea. Basically, once they got over being scared to death they started beating the snot out of each other. I had to start on live foods, then they were just finicky, and finally they were weaned to the eating machines they are today.
Once in the large display, I could see better behavior. I seem to have 2 males and 2 females. The 2 males fought a lot; the one I would call the "winner" (less injuries) nonetheless was the odd man out. Recently, one of the "males" starting showing a very fat belly and I thought he might be a she, but it turns out he was just putting on a HUGE growth spurt. Within days he easily became 20% bigger than the others. (Or she. As long as the fish can tell the difference.)
I haven't seen any fighting since. I guess they sorted out the pecking order, and I'm surprised the odd male out survived -- but he had plenty of places to get away and lots of room.
There may be some of that last Oz shipment still out there. These are not immensely popular fish, which is a shame since they are so pretty. Based on my experiences, I would suggest a generous sized breeding tank to get started.