Must be nice to afford a Leica for B&W, i.e. grayscale work!
However, apart from converting any old image from color to grayscale, there are other cameras that can do that.
One such is the mighty Foveon where one raw pixel is derived from three sub-pixels stacked as layers on top of each other ... no Bayer demosaicing to get color is necessary!
Here they are:

The good news is that each layer image can be extracted from .X3F raw files separately as a grayscale image with a built-in filter. For instance, extracting the "red" layer gets you a grayscale shot with a sorta Orange filter, whereas the "green" layer approximates a CIE "Y" response.
Early Sigma Foveon cameras can be quite cheap you-know-where and the so-called "Merrill" models' proprietary raw converter can extract all or any of the three layer images and even mix them together.
