NBME Practice tests for CK??

I remember taking them for Step I, but apparently all I can find for CK is the practice material provided on the website. I signed up for a practice session at Prometric. I really want to take two practice tests, but I am afraid if I schedule it twice then I will just be presented with the same test.

Does anyone know if there are the NBME online tests you can take at hom for Step 2, like the ones you could purchase for Step 1?