Many, if not all of the seats found in the co-op, farm stores or tractor stores no longer are UV material protection. You'll be replacing the expensive seat in about 5 years time once again. I'm not the only who had been thru this in the past 7 years, many others have too.
I did some homework. Realized the Marine seats are still UV protected and are very comfortable too. Wise is one of the leading seat makers. These come in many colors patterns and mounting.
This style is called the Wise Blast Seat as an example. Here are a few to consider if your Satoh is white and blue. It white and red, just pick the color change when ordering.
The Wise classic High Back in blue,
Here is their low end for about $29 at Walmart.
All seat fold and have the 4 standard mounting points on the base. Additionally, there is a base swivel one could buy to help easily hop in/out of the seat or to turn to look behind the tractor.