I bought a Kolpin off Amazon for my Kawasaki Teryx several years ago. It doesn’t fold flat, but the bottom flips out for plenty of breeze.
Be aware that you get much dirtier riding with a windshield than without, as the vortex created by pushing that big plexiglass sheet through the air creates a vacuum that ***** trail dust from behind the machine.
Serious riders add a second window behind the driver, or wear full face helmets and neck scarfs, then take a shower when done riding.
Casual riding at low speeds across the property or on the paved county road or vegetation presents no issues.
My Kolpin was “used”, ie a return, with a damaged box and a steeply discounted price. Everything in the damaged box was in excellent, unused condition, with no missing parts.
The glass windshields have been getting more popular since I bought mine, probably at least partially because the machines have been getting more powerful and faster. Mine flexes a fair amount, but I’m not into high speed thrill riding. A Mule is more of a utility machine than a racer, sp polyacrylic is fine.
Definitely get one that opens for airflow. It gets pretty hot in there otherwise.