This is not an exhaustive list; however, it may be a good start:
Choice Support – how sexual violence can affect people with learning disabilities and autistic people
RESPOND – supports people with learning disabilities, autism or both who have experienced trauma in their lives
SARSAS – Learning disability and Autism support
AUTISM RESEARCH INSTITUTE – Sexual Victimization in Autism
Stop it now – Have you been abused?
One in Four – support survivors to recover and heal from child sexual abuse, domestic violence, and trauma
Sexual Abuse and ADHD – Sexual abuse and ADHD Resources
TACA – Risk Reduction Strategies for Physical and Sexual Abuse
ASERT – USA organisation with a HUGE article/resource section – Be Safe Resource Collection
National Autistic Society – Safeguarding Young People on the Autism Spectrum (Downloadable PDF)
Autism and ADHD Articles
These articles are not peer-reviewed and are in the public domain, so make sure you question their findings/opinions for yourself and do some more research on anything that hits home:
Prevalence of Victimisation in Autistic Individuals: A Systematic Review and Meta-Analysis
Disability Hate crime statistics
Evidence That Nine Autistic Women Out of Ten Have Been Victims of Sexual Violence
The Tragic Truth About Sexual Abuse and Autism
Experiences of interpersonal victimisation and abuse among autistic people
Child sexual abuse: keeping autistic children and teenagers safe
How Does Autism Affect the Processing of Child Sexual Abuse Trauma?
How to Protect a Child With Autism From Sexual Abuse
Predictors of Sexual Victimization Among Autistic and Non-Autistic College Students
Sexual Abuse Online – Helping My Autistic Child
The Effects of Child Sexual Abuse on Children with Austim
The Link Between ADHD and the Risk of Sexual Victimization Among College Women
ADHD: More than half of women with ADHD have experienced Sexual Victimization
Children with ADHD have considerably greater odds of being victimized in reported sexual crimes
Adolescent Sexual Victimization, ADHD Symptoms, and Risky Sexual Behavior (PDF Download)
You can see a long list of support resources and links, a NSPCC FAQ, and a what can I do section.