Just when you thought the fourth movie toys were finally all done, TakaraTomy decides to throw out one more for the hell of it... and it doesn't come out until August 3rd, which is a year after the movie was released in Japan, for about 8000yen. (about AU$90 atm)
It looks like this black redeco of the AD-31 remoulded Optimus toy is a ToysRUs exclusive in Japan, so might be even rarer to find than the AD-31 toy, which is hard enough to find as a "regular release" toy. (it's one I'm still looking out for, but online stores were very light on the last few movie toys, and sold out fast)
The official name of the toy is "Toys R Us Limited Transformers Movie Advanced Series Black Knight Optimus Prime".
Images mirrored here for when the TRU listing is eventually taken down.