SadieNan, I too hope that someday Cathe will make a stand-alone step kickboxing workout.
She has step kickboxing as part of the power circuit segment on her Cross-Train Express series workout "Power Circuit". There are also step kickboxing segments (two, I believe) on "Low Max", and one 5-minute step kickboxing segment on "Circuit Max" (on the same DVD as "Cardio Kicks").
A-Jock