We have what is probably the same sofa with air mattress that you have, or very similar. It was made by Flair. Within the warranty period, our mattress completely failed, and our dealer ordered a replacement. It came in, and not checking the size, ultimately discovered it was the wrong size. Not wanting to mess with the dealer, I ordered a new one directly from Flair, which we still have and use occasionally. I just checked, and the website (
https://www.flairoutlet.com) is no longer functional, so you may be better off either replacing the sofa or getting a good air mattress from a sporting goods dealer.