It is an acrylic plate with clear acrylic ball in the center. Please prepare the tube parts yourself. Because it is made with acrylic material, the image quality would be deteriorated compared to that of made with optical glass.
clear ball: diameter: 20mm, acryl
clear plate: diameter: 70mm, aryl
Check out the page below to find out how to make them.
→ How to make soratama by yourself
Available at shops below: