Need help with an old Briggs and Stratton

[jfkbengals]

So I have a Murray push mower that I believe dates from sometime between '85-'95. It was collecting dust on a shelf in the back of the shed for about 14 years. The misses set up a garden area that doesn't allow use of the rider, so I pulled it out to maintain that area. I turned the blade by hand to break any seizure in the cylinder, added some fresh gas, and pulled the cord. Started right up, but runs pretty darn rough, so it is need of a tune up. The plug will be easy enough to replace, as it will have identifying marks that can be used to match up to a modern equivalent. My problem lies in the foam air filter. It is super dirty, but also kind of dry rotted, so I can't just wash, dry, and oil it. It needs to be replaced, and I can't seem to find any part number on the housing. The engine says Briggs and Stratton Magnetron, around the pull cord vents, and there is nothing else I can find to identify the model of the engine. The Google machine hasn't been much help, nor has the B&S website. There was one filter I found on B&S that stated it was for model years around that time, but the item pictured is not the same shape. Does anyone have any knowledge on how I can find one?