I believe Calumet in Chicago has them in stock and will ship.
Google for the Kodak TMAX Direct Positive Kit and a few places will ship although B&H has the best price.
You will get the best results with a film that has the clearest base. I'm assuming that kit gets rid of all the magenta stain in the Tmax base.
I have some Legacy Pro 400 that has a very clear base and also some of the Foma (T200) films do also.
I've been wanting to give this shot too so good luck.