Scroll down close to the bottom of the page... this OSD board would probably work well with the M4/N4 combo. I'll probably use one when I do my M4 / Joerg's BLDC 250mm blackout type quad. Besides that, I can't recommend freebirdrc enough. Great prices and fast shipping.
http://www.freebirdrc.com/#!parts-and-hardware-etc/cy2m