I am here on a F1 visa and my insurance is paid by my university. Can I purchase a student insurance plan for my dependants?

International student insurance is available to international students and their dependants. The dependants are not eligible to purchase the insurance for international students if the student does not purchase the plan.

In your case since the insurance for the international student has been paid for you can consider one of the several visitor medical insurance plans that can cover visitors on any visa to the US. Another choice would be to waive out of your student plan and purchase a international student insurance plan for the whole family.