An interesting (and cheap!) source for large-diameter quartz/fused silica tubing - these are quartz "sleeves" for use in water purification systems. For more info and pictures, see my page at: http://imajeenyus.com/mechanical/20151127_quartz_sleeve/index.shtml
This is a video comparison between the Gardensun Glass Tube and the Gardensun Quartz Tube. As you can see in the video, the glass tube will crack when it is on and water is spilled on it. The quartz tube, on the other hand, did not experience such problems and did not crack even after watering it for over a minute.