Also anyone know if Bandai has plans to do the Geara Doga and Geara Zulu in 1/100 scale?
Can't really advise on US retailers as I mostly shop from HLJ...
As for Geara Doga, etc. in 1:100 - there have been no announcements about such products. So the kits could come out six months from now, or we could still be waiting six years from now... Impossible to tell, really.
I guess if the Geara Zulu continues to play a reasonably prominent role in Unicorn there's a decent chance it may come out in MG within the next few years - but it's all just speculation.