Airpulse PK2 Wheelchair cushion For Son

We have two sons with Spina Bifida and Autism. Our son, Jesse, is 38 years old and lives at home with us. He has had a bed sore for over 1 year on his bottom. He is thin and has no natural padding. It bleeds several times a week and just will not heal completely despite constantly dealing with it under a wound-care specialist. Jesse has had bed sores in the past which we have had to heal by keeping him immobile for weeks in bed. He goes to a day program and works for three hours a week there which requires him to use his wheelchair. I found a wheelchair cushion that would help to heal the sore and prevent any further sores but it is over $3900. Medicade absolutely refuses to pay for this cushion. Other cushions have not worked to let this sore heal. He goes to Spina Bifida Camp in July and will not be able to swim with this sore and if it gets worse he will not be able to attend camp at all. We also have an important family function, our convention in Detroit, after camp in July. I am frantic to get this healed by then. We need help to buy this cushion, please.