Asking on behalf of a friend: Does anyone happen to know if replacement arm pads for wheelchairs are available? A web search is proving fruitless & it looks like a DIY project or repurposing of a related product may be in order.
Try asking first from the local company that provided the wheel chair, else find a distributor by contacting the manufacturer of the chair otherwise your likely to have a DYI. Also, you might be able to find someone who does furniture upholstery in your area, they could likely do a fine job for not too much money. I built a new arm for my sons power chair to hold his books and provide him a second point of leverage to help him stand when exiting the chair. Good Luck