You could make a curved PVC frame covered with thick plastic film. Here is a good description of a plan. They say it costs about $100 to build, but that's in 1996 dollars, I think, because it looks like that's when this was written. Expect to pay more, but not too much more:
Check with your local lumber yard or window supplier. many times they remove old single pane sliding doors just to discard. Construct a wooden frame to support the doors and you have a glass house. Just do not throw stones!