You would want to find a Speech Therapist: here's what google says they all do.
"a speech-language pathologist (SLP) is essential for helping individuals with communication devices, as they assess needs, select appropriate Augmentative and Alternative Communication (AAC) systems, program and train users on the device, and provide ongoing support and modifications. SLPs collaborate with families and other professionals to ensure the device is functional and integrated into a supportive environment.
How SLPs Help with Communication Devices:
Assessment:
SLPs conduct thorough evaluations to determine if an AAC device is suitable and to identify the specific communication needs and abilities of the individual.
Selection:
They help explore different AAC systems, including low-tech and high-tech options like speech-generating devices, to find the best fit for the person's unique requirements and goals.
Training & Implementation:
Once a device is chosen, the SLP provides training to the individual, their family, and caregivers on how to use, maintain, and get the most out of the device.
Programming:
SLPs program devices with appropriate vocabulary, including core words (used in everyday communication) and fringe words (specific to particular activities), to ensure effective communication.
Access Methods:
They can teach various access methods for devices, such as eye-gaze technology, switches, or help from other people.
Ongoing Support:
Communication needs can change, so SLPs provide ongoing management and modifications to the AAC system to ensure it continues to meet the user's evolving needs.
Collaboration:
SLPs work with a team of professionals and the user's support network to create a comprehensive communication plan that is supported in all aspects of the person's life.
Funding Assistance:
In some cases, SLPs can assist in identifying funding sources or help complete paperwork for insurance companies to cover the cost of communication devices. "

And remember....he might be crying out or showing signs of anxiety like a 5 month old, but that could be because his brains ability to bring speech thru the system and out his mouth is not connecting properly. Thus doctors will often just assume it's severe cognitive delays and there is no hope. People on the autism spectrum have dealt with this all their lives with people thinking they have no intelligences when it's just they have no way to communicate when they are non verbal and so they stick to what they know--usually crying or lashing out physically to make a point or get what they want/need. They truly don't know what's going on inside and it's certainly worth a try as all humans have a need to communicate on some level, it's just not always with spoken words. Babies, even as newborns, communicate the best they know how and that's with crying right?