None of the six original seats I have for my car have any such mesh in the foam, I assure you. There are chunks bigger than my forearm missing from the driver's side seatback along with significant damage to the bottom as well. If you were to bring a chunk of what you have to an upholstery shop and tell them, "I need the new version of this" they'd be able to get it. However, due to the fact that your seats are as bad as they are, you must also remember that you're now probably going to have two different densities of foam. Some areas of the seat will be firmer than others; it will feel lumpy when you sit on it.
As far as everyone's seat foam breaking down, I have five excellent seat cores here that would beg to differ. Only the driver's seat was bad. It's not the original one for the car and had been sitting outside in a field since the 1980s, exposed to rain, heat, insects, rodentia, etc. It was so bad the listing wires literally rusted away. There were only two left in it; the rest were brown powder and stains. What's left of that foam is actually still pretty solid, amazingly enough. As I said, there are just enormous chunks missing, and the seat springs and some of the frame are rusted away.