Jerry, my guess is in two parts. If the existing seat still has good upholstery and padding it might be relatively easy to rebuild the seat. Once the seats are off the base they are easy to work on.
But if that is noit a reasonable option I cannot think of why a good captains chair from one of the high end SUVs would not work well. You might have to create a new base but that would not be hard.
Don’t forget to check with converters like Marathon to see if they have any spare parts or better yet seats removed when they did an interior refurbish. Contact them all. You never know what they might have sitting around.