I thought about getting another one, but that would cost $80-100. Instead I decided that I should attempt to repair it.
I went to Home Depot and picked up ten 10' sections of 1/2 PVC pipe and a number of 'T' and corner connectors.
I started by removing all of the bent and damaged parts of the greenhouse.
Then I created two arches out of the PVC pipe. One for the front and one for the rear.
I used zip ties to connect the arches to what was left of the greenhouse structure. The shelves are still usable.
Then I added a section of pipe to connect the front arch to the rear arch. I don't know if this was really needed or not. I had the pipe and the fittings so I figured why not.
The final step was to create the ridge beam to hold up the center of the roof. I used a 4-way cross in the rear. This allowed me to run a center support down to the ground.
Here's a view of the front. It does not have the center support. It would have made getting in and out too difficult.
Here's what it looked like when finished. I think it'll work.
It was a tight fit to get the plastic back on. I managed to rip a hole in the corner that I fixed temporarily with duct tape (as seen in the picture above). The duct tape didn't work real well and I had to sew the corner with some thread.
When I conceived of this project I imagined all kinds of cross bracing. As I was putting it together I realized that it was going to be unnecessary. Simpler was better. That also means that I have a bunch of PVC pipe and fittings left over. Oh well, I'll probably find something to do with them.