There is currently no practice C.S.P.T. practice exam which I am aware of that is separate from such online sterile-prep programs. There are some free related questions and content online out there however: https://quizlet.com/123856903/cspt-2016-test-1-study-guide-flash-cards/94
I recommend the book: Mosby's Sterile Compounding for Pharmacy Technicians: Principles and Practice (Sterile Processing for Pharmacy Technicians): 2'nd Edition.
Also, the P.T.C.B. has its C.S.P.T. exam content outlined: https://www.ptcb.org/guidebook/cspt-exam-content-outline#exam-content-outline32