Really right stuff made a plate for the mark 1 version. I called them about the mark 2 version. They said they wanted to gauge the market before making a plate. If everyone can request it from them they are likely to produce it.
I already asked RRS about it. They informed me that they were not going to make one. Time will tell if they change their mind.
I really hope that isn't true. The RRS plate for the Mark I really made the camera for me. I even assumed that Canon's redesign of the flip-out LCD was a nod to all the L-bracket fans who were put off by the swivel design of the Mark I.
On the other hand, if RRS stays out of the market, someone else will likely fill the void. Ebay and Amazon have a number of low-cost Arca products available now.