I don't know of anything specifically that awards aid to nurses for continuing education / refresher courses. I do know that many schools offer aid opportunities, and the cost for 1 or 2 courses can vary quite a bit, so this is also something to consider. Private loans are sometimes an option for those returning to school, but may require at least part-time enrollment, and because you are not looking for a degree or certificate program, just one or two courses, you would need to figure it out with the school and lender whether or not you would qualify.
What type of refresher course are you trying to take? What type of Master's program are you eventually trying to place into? I suggest finding the schools you would consider attending, offering the course you think would help you progress in your career, and then contacting a representative from each school to ask about repayment plans and other aid available or loans.
I would also suggest to try contacting a local community college. The costs can be quite affordable (as low as $50 a credit hour) and may have what your looking for without the needs for additional funding.