Hi,
I am in the same situation you are in,I am currently looking for a Dental Assistant job while preparing for my Board exams.I decided to take the X-ray exam after I attended many interviews,they all told me I should take the exam.
In my state,NC,you contact the School of Dentistry,I'm pretty sure its the same with your state,contact them and ask for the Dental Radiology exam.🙂
Hope everything works out fine with you,bye