A tree swing hammock chair.
I got one for a gift.
But as I was researching it via Amazon, it was interesting that many of the reviews were from parents that have an autistic child. They said how it was a good relaxing thing for them etc.
Just as an example:
If you read the reviews of this item, you will notice some from parents of autistic kids.
I don't know personally about this.
So this is just what I have read.