I would (as a General Nav instructor) recommend you acquire a CRP-5 simply because this is the instrument on which the answers to the exam should have been calculated. I am unfamiliar with the CRP-1, but it may have limitations, and some instruments have scales slightly different from those on a CRP-5. I found a considerable difference in the temperature rise scale of a different flight computer, when compared to the trusty '5'.
Best of luck with your course, and enjoy Bristol. A good school.
SC