Real cheap fix- get a Sit N Fly seat cover, XXXL size and then the only thing you would have to do is do a small cut of the material in front and use a strong stapler to affix it to the front of the seat pan. I bought an ST seat (non OEM) and covered mine recently- $30 shipped from eBay vendor and to me it looks very good (plus in the summer, you get airflow under the bum…in the cooler weather, it’s not cold under there since you have fairing protection).
Here’s some pics:
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I have a similar cover on the scooter seat and Air Flow branded covers (more expensive) on the Saddlemen seats I have (I like these because of the airflow in the hot weather so you don’t get swamp butt). It takes a little work to get it just right on the seat, then you have to basically make the material ‘learn’ to be compressed at the front and back. Worked well for me, and the price is right. If you wanted to get the existing seat repaired, there are some mobile services around that do that kind of work (mobile upholstery repair), but I’m not aware of the cost. What I sometimes do is pull the material off the back of the seat, latch the seat in place, then just easily put the elasticized material back in place - works perfectly.
I agree with others here to seal the gaps first so if/ when the seat gets wet, it won’t get into the foam and get moldy. Here’s an eBay link for the cover:
https://www.ebay.com/itm/133013363544 - seller is paulibiker (I have no affiliation with the seller, just good experiences based on prior purchases).