You may not need a lawyer at all. If you are notified that you may be the subject of disciplinary action you may need a lawyer and that would be a lawyer with a thorough understanding of employment law who can protect your rights. Employment policies should protect both the accuser and the accused. The lawyer should also be familiar with, and able to advise you on the issue of defamation.
In my opinion you need an employment law specialist with many years of sexual harassment experience. You also need a lawyer that you trust and feel good about working with. Remember that you will be disclosing very intimate details of your life to your attorney because this is a sexual harassment case. You might find a lot of the questions personal or maybe even embarrassing. Find an attorney that you feel comfortable with telling your most intimate details to. Contact your state or local attorney bar association and get referrals from them. And interview as many lawyers as you need to until you have found the right one for you. Many lawyers offer a free consultation so take advantage of that. Good luck!