These women are out there, and DO exist. HOWEVER...They are rare as hen's teeth. And never seem to develop into more than just sex partners.
I would say that you keep telling women that you are married. This shows honest, and that you are proud and not afraid to show off your women or woman. Stand proud, and stand tall. If you form a relationship on a lie...Then it will always be just that....a lie. And she will wonder what else you are hiding from her.