I believe this is it.
https://www.google.com/search?q=book+holder+for+wheelchair&client=safari&hl=en-us&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiiobDwqPHNAhWM6yYKHX34BmMQ_AUICCgC&biw=1024&bih=671#imgrc=qP0ExlhBiz5-RM%3A Larry Willis Retired and proud of it