OK resourceful people. Time to design a replacement car seat. Include a padded seat. You will have to drive with your pants down though.
Then if someone tailgates you FLUSH!
Don’t laugh, but I have carried a bed pan with me before on long trips. I have an intestinal issue that can make traveling hard. My wife and I bought a conversion van took everything out of the back and built in an RV toilet with enclosure. It’s very nice if I do say so myself. Ahead of the curve I guess, but I still prefer a real rest stop/truck stop bathroom.