I don't know if there are associations perse but there are plenty of forums.
Suggest you find a seasoned male nurse to mentor you. My experience is this: a nurse (specially a new one) with a chip on his shoulder reaps what he sows.
My male colleagues over my past 27 years in nursing are not generally overwhelmed with gender bias issues...they're too busy doing their jobs. A nurse (whatever gender, ethnicity, etc) who does a good job and is a teamplayer does well in nursing. Just my 2 cents.