The stock exhaust that Highway Stars sells may work for you if you can't find a used OEM unit, but you may only be looking for the muffler as listed in your post.
How soon do you need it? I plan on pulling my stock exhaust off soon (which I'm fairly confident is solid and in very good shape). My car is a little more rumble than most because the cat has been hollowed out since 1988 or so.
I need to confirm condition, but, the car has always been garaged and it's rarely ever seen inclement weather. I know the tail pipes and all are in perfect shape.