That you "need to get the certification" somewhat suggests that your employer "wants you to get the certification", in which case they should pay for it.
Otherwise if you want to get it with a view to improving your chances of finding a new job, you might just have to grin and bear the cost.
Generally you will only get discount coupons for the CX-310-200 and CX-310-202 exams if you sign up for a training course with Oracle or one of the other big providers such as Netcom. I have never come across discount coupons for these exams in the wild.
In "Sun times" there were also discounts for some universities (free access to study materials + cheap voucher). And they were quite large, like 90% off the official price.