Back in the mid to late '80s I shot quite a few body builders. I was rehabing from an accident, and went to the local gym to do some strength training, and met some. It worked out great for me, as I was short on cash from my accident, and for them, as it gave them reasonably priced photos of themselves(vain lot) for promotions. BTW, its a great way to gain experience in portrait work, as well as studying the human form(awsome women!). I would recomend you go to a gym and meet some , and offer your services.
Rick