The Hi-Perf should be available alongside the Pattern version. I order direct through to Hirobo as I have a personal arangement with them. The Stream 90 (HiPerf and Pattern) is now available and is really quite breathtaking in quality. I have a YS110 coming for mine.... . For AA or 3D you really need a YS63 for the 50 and a YS110 for the 90. For Pattern probably a YS53 or a YS90 for the 90 size. I know people have used 2 strokes and found the 4 strokes a better option.
In the US I really don't know who you would contact, I guess any Hirobo main dealer will do, if they haven't then they can get it!
Oh.. I also have coming a carbon u/c set for the 90HiPerf. It should be real nice, the Hirobo heli carbon parts are superb.