Association of Transcribers and Speech-to-text Providers (ATSP) offers a directory of people and agencies.
National Court Reporters Association (NCRA) has a directory of certified members.
Described and Captioned Media Program (DCMP) houses a list of vendors, mainly for captioned media service providers, but some companies offer real-time speech-to-text services as an additional service.
Many states have state affiliated agencies supporting deaf and hard of hearing people that offer information and referrals to speech-to-text providers.
Subscribe to the NDC Listserv and seek additional service provider referrals from colleagues.