So I am just a guy on the internet, not an expert, but did you look into using "Amara"? It's not completely clear to me but it seems like it might be possible

So I am just a guy on the internet, not an expert, but did you look into using "Amara"? It's not completely clear to me but it seems like it might be possible to get volunteers to do the transcription. They also claim to offer lower cost professional captioning services, too. http://www.amara.org/en/ http://www.amara.org/en/ If you do contact them, please consider sharing what you learn--I'm completely ignorant but willing to learn, and you might help the next guy. Good luck!