Pentax is making one that is said to be available in Japan.
I have a 645D and a bunch of 645 lenses. I cannot find a Pentax 67-645 adapter. Said adapter would allow me more choices in the used lens market. With the popularity of the 645D and a run on 645 used glass, it would seem benificial (and profitable) for a 3rd party to make such an adapter, such as Photodiox. Is the 645 mount still under patent?