Wheelchair seat cushion. (Southport PR9)

I had been looking for a wheelchair so I could take my elderly Mother-in-Law out to get some much needed fresh air. Someone has very kindly given me a wheelchair now but it has not got a seat cushion and so I am asking if anyone has one that they no longer need. It will make a once very active rambler able to enjoy the outside world once again. Thank you in advance, Kevin.