normal prime for Pentax 645N with best possible bokeh, native or adapted
Since I bought my Pentax 645N during spring this year, I have been using my F100 less and less as the Pentax took over my hole field of nature photography, leaving the F100 for light travel and carry around.
One thing I am missing tough is pretty bokeh. For most of my shots I use the Pentax FA 75mm f/2.8 as I am a big admirer of the normal perspective. While my Nikon AF-S 50mm f/1.4 is not a perfect lens in terms of bokeh, the Pentax leaves a lot to be desired in comparison. For instance, take the image in the attachment. Shot two weeks ago, using the Pentax 75mm set to f/2.8, wide open. I wouldn't call this smooth and I really wish it could be improved.
Is their a prime lens in the range of 70-90mm that offers a significant improvement in bokeh and can be adapted to the Pentax 645N?