It hasn't been covered on the BN. White Labs does make a Sake yeast, your LHBS should be able to special order it for you, it's likely not something they carry on a regular basis. As far as sourcing true sake rice, I have no clue where you would be able to get that from. Sake is made from the inner part of high quality rice kernels. If you imagine taking a kernel of barley and sanding off the hull and the outer most part, that is essentially what is done with the rice. The higher quality sakes are made with rice that has been milled further, containing JUST the starch center. This means that it takes more rice to make, and is thus costs more to produce. Lower end sake uses more of the kernel, which will contain more proteins and lipids. You will also need koji mold, which functions in breaking down starches (since rice doesn't have it's own diastatic power). You'd have to source this separately, potentially places selling koji may also have a line on sake rice for you too. The White Labs page for their Sake yeast has an example recipe, it looks like they are just using regular rice though...
http://www.whitelabs.com/beer/strains_wlp705.html