I don't have an actual Kodachrome IT8 slide, but I do have the spectral data. If you happen to have spectral data for your camera/scanner and light source this is just as good as an actual slide!

I've attached that along with an Argyll .ti3 file that I made from the spectral data. If you download a demo copy of the Basiccolor profiling software there are a ton of reflective and transmissive target data files included in the app contents, many with spectral data included. Hope that helps!