Hmm, I'm about a B cup, so while slightly larger than you I still find I have this problem from time to time. I've had good luck with the Bristol6 heart shaped pasties. They're available in multiple designs and colors and the website has even more. For me, they've been able to cover my nipples with ease, and also left enough of my boob showing to not make me feel like I might as well have just worn a bra.