The Occupational Safety and Health Administration (OSHA) requires employers to provide all workers — including transgender employees — with prompt access to a clean restroom. Additional requirements related to restroom facilities and bathroom break policies are outlined in OSHA's sanitation standards (29 CFR 1910.141, 29 CFR 1926.51 and 29 CFR 1928.110).
You can contact OSHA anonymously regarding violations and are often protected from being fired in retaliation.
It's free to call and their job is to string up companies in violation, so they'll be happy to walk you through everything.