I;m not sure if this will work or not but it worth a try. Have you tried sprinkling backing soda in his room? Baking soda eats odors and is inexpensive.
I would get a box and sprinkle all over his carpet or floor if there is no carpet and leave for at least an hour if not overnight. Like I said I don;t know if this will work but I think it will at least get the smell out. Don’t know how to sanitize.
Our cat just decided to start peeing on our bathmat like very day so we are washing it every day. We’ve even started hanging it after we use it but as soon as it’s down again she gets it. I think we are just going to have to buy a new one.