Help give Mason a voice

Mason is my 4 year old son. He has been diagnosed with autism and is currently only about 5% verbal. This means he can only speak about 5-10 words. We have worked on sign language and he picked up some basic signs but due to his delayed motor skills it is hard for him. His developmental preschool started using a program called Proloquo2go and he loved it. For the first time he had a voice. Not only could he say what he wants and needs, but he started to pickup words from listening to it speak for him. I would like to get a device for him at home but it is hard and expensive. The program itself is 250$ and that doesn’t include an iPad or other device to run it on.