When I did the double clinic a couple of the rowers asked about the seat cushion that I was using. I got it from Amazon and here is the link. It is about 25 dollars.
https://www.amazon.ca/gp/product/B06ZYN1GY7/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Thanks Louise. I had heard a "buzz" about a seat cushion so now mystery solved!