I would also encourage you to seek the help of a BCBA or related therapist who has a specialization working with individuals with ASD. Seeking advice from non-professionals online about types of interventions that may have worked for other children can be ineffectual or even harmful when tried with your son, especially with improper treatment adherence. If he does not already have a therapist with experience working with children on the spectrum, I would start there.

If you want to do your own research on effective treatments regarding fears and phobias for young people with autism spectrum disorders, there are a number of peer reviewed articles from professional journals that have effective interventions. You can do some reading and become better informed when discussing with his therapist about what would work best for him. I looked up two articles myself to get you started. These are for discussion only.

Research in Autism Spectrum Disorders, Vol 59, pg 58-67 - discusses an effective intervention using flat screen computer-delivered virtual reality and cognitive behavior therapy.

Journal of Applied Behavior Analysis, 2006 Winter, 39(4), pg 445-448 - evaluated contact desenstization as intervention for specific phobias where the treatment made access to preferred objects contingent on gradually increasing approach responses to phobic stimuli.

If you are also looking for parental support groups, there may be one in your area and I would look this up. Parental support groups for children with ASD can be very beneficial in seeing you through this.

I can't offer a specific solution the any of the above but it may be helpful to try and understand the underlying reason for the fear or phobia. I have put in a link to the National Autistic Society, based in the UK, which has a terrific array of strategies and suggestions to try and deal with all aspects of sutism. It may give you some ideas and is a great resource generally

[autism.org.uk]