Look at your health insurance, they may covera certain number of sessions with certain people in network. It may not be super convenient, but it may be something that gets resolved rather quickly.
The other option is to go over the teacher's head. Don't be afraid to do this. But before you do look at what other impacts it is having on your son (go observe in his class, start asking him some questions). Does he readily participate in class or does he hesitate? Does anyone comment on his speech? Is he at risk for being teased? Look at the social aspect to see if the social is or could begin to impact his academic. Take some notes and have them ready. Call the office, ask to have him tested for speech needs, then follow the phone call up with a hand delivered letter on a day or so that is DATED! (make sure you keep a copy for your records and get a little notebook to write down all that you do. Write down a summary of every phone call, who you talked to, date and rough time.) If you request testing IN WRITING, with a dated letter they have to do something because it legally starts a timeline for them.