I had a pretty severe tear in the top of my BX 2200 seat a year or two ago. I used 100% GE silicone caulking, color black, and put several layers over the offending area. It's not perfectly smooth but it functions perfectly and at this rate I'll be able to use the seat for several more years before I need to worry about replacing it.
A tube of the 100% GE silicone rubber caulking cost about six bucks with tax. Try it you'll like it!
Unless you want to perfectly smooth surface that is
I am sure it would be possible to make the surface smoother. I did not bother as I was not sure the silicone caulking would work...
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Bill