I had a similar problem. In my case it was the sports style wings on the side of the driver seat that wore through. I got quotes from two dealers, new seat cover £120 + 1 hour to fit. Asked the village garage it they knew anybody else and got the number for a freelance car upholsterer. He took the seat out, removed the cover (it's pulled tight not glued), unstitched it and removed all the plain black and replaced it, then refitted the seat for £60. Best part was he used a cloth that looks the same as the rest of the car but is considerably thicker and harder wearing. Much more suitable especially as most of my trips are commuting one-up. If you didn't know you wouldn't notice any difference. If the foam's gone that might be a different matter all together as it may (and I don't know for sure) be integral to the seat. Modern car seats are made in a totally different way to those 20 years ago, and far better for it. I guess the message is, if it's not too late, get the cover fixed before the foam goes. You should be able to get the part no from a dealer. Or it might be cheaper to get a replacement seat, at the prices I found. Especially if you can get one from a breakers yard, but need to be sure it hasn't been damaged in any way and lost any of the protection it provides. Good luck!