Bring your own seat cushion (very firm!)
For all you short people....I have for years now been making seat cushions for the gliding club FROM STACKS OF NEWSPAPER! Wrapped in plastic tape.
And covered in a nice cloth cover. So the cost is ZILCH. (except for your effort).
Your seating must be NON COMPRESSIBLE. Try standing on a newspaper cushion, and it will NOT compress! And you can make it as high or low as suits your preference.
Just try to remember not to leave it out in the rain.....