I dont know about the nissan factory touch up paint, but i know duplicolor makes a great matching paint. Ive touched up numerous spots on my car and u cant even tell the difference. I think its like 5 bucks a can a pep boys.
-Blair
I also have a feeling that official Nissan touch-up Cloud White from the B16 2000-2006 Sentras would work on the B14. It looks to be a flat white as well.