Color T/R Densitometer Calibration Plaques (Xrite 811)

Title says it all, I need to calibrate the color channels for status a and m, transmission and reflection and how idea where to find wedges with known values. Any have any ideas?

My Tobias calibration is made from film and they offer up the density for each channel. As you can see, the color densities nearly match the white density. I suspect a Stouffer calibrated wedge may be similar (that is the color channels very close to the white channel, even though when you get the calibrated wedge, there will be no color information).
Other idea is to use a neutral density Wratten filter (or other thin filter). After calibrating the white channel with the Stouffer wedge, test the ND filter and assume the color channels will match the result you got from the white channel. Assuming it is a true ND filter.

Thanks ic-racer! I have got an old kodak one with the color channels, the stouffer one didnt come calibrated with anything other than visual, of course they are close but I wanted to just start off on the right foot. I eventually got my local cinema print lab to calibrate them for me against a xrite 310. Does anyone still make these new? In the future ill eventually have to buy new plaques.