A parent training model for toilet training children with autism.. This could be worth looking at if everything else that you have tried just doesn't seem to be working or if you are the kind of person that like a plan and following something quite strictly would suit your child, or you, best. It take a little bit of reading to get to grips with.
Visuals... I am about to post a second post with a few bits and pieces that we used ourselves. Including a very pretty little bathroom schedule board, if I do say so myself! But, as ever, you can go straight to the "symbols" link at the top and get a few individual symbols to download... I am just adding a new section for this as we speak. (Please note, the symbols I am about to share on the Symbols link, will differ from those within my next post... so do take a look at both and see which will suit you best!)