Braxton’s alternative seating chill chair

My son, Braxton, came to live with us when he was almost 2 years old. We knew he was special from the start. He has a way of bringing sunshine & joy into a gloomy room with just a single smile. He has Periventricular Leukomalacia caused by several brain bleeds that he had a birth due to prematurity and maternal drug use. It is under the umbrella term of Cerebral Palsy. He is unable to sit up on his own and mainly has a wheelchair that he sits in. I want to give him another option for seating upright due to his reflux that is more comfortable to watch television in or play, but we can't afford the chair at its current price. Any help would be appreciated. Thank you, Katrinia M.