Just found this Changing Mat on Kiddicare and I thought that it might be useful to someone. The following info is taken from the description on the website:
'The unique design of the RabbittsTM Mat makes it an ideal choice for the parents or carers of special-needs children whether handicapped, paraplegic or autistic. A child can be cleaned and changed without needing a second person to assist, by placing them on the mat with the integrated shoulder / waist harness holding them firm'.
It costs £24.99 and can be found here:
\link{www.kiddicare.com/invt/cmatrabsafmatbcrm}