On program that offers grants is via http://www.generationrescue.org/
Also TACA( Talk about Autism Now) offers some support and grants.

This may help you, there are grants available however they take a long time and you are going to be up against a lot of other people to get them. The best thing to do is contact state agencies like departments of developmental services in your state, or any other state agency for disabled people. You may not find ASD specific agencies but your child does qualify as being did baled
autism-reimbursement-grants.html