A new curriculum called “Healthy Relationships and Autism” is now available from Wesley Spectrum (a behavioral health organization with several locations in the Pittsburgh, PA area). It was designed to teach skills to adolescents and young adults with Autism Spectrum Disorder or cognitive challenges in the areas of self care, sexuality, and relationship development. Their website has an example lesson to help you determine if it would be right for your students. They do not publish their pricing information (you have to email them for more information but they will send you a sample packet).
I have not used this curriculum but there is some evidence of it’s effectiveness. A study published in School and Educational Psychology evaluated this program with six students. These students showed increases in sexual knowledge which they retained one month after completing the class.