Greenhouses, Sheds and Sun Rooms - clear flimsy window replacement in sunroom

My parents have a house that was purchased about 20 years ago. It has a sunroom off of the master bedroom. The windows of the sunroom are made of a clear flimsy vinyl. This material is much like that of a clear shower curtain. During our latest hurricane, every window was torn by falling tree branches. We have spent countless hours on the telephone trying to find a contractor to replace the windows, but no one works with this material. One individual quoted us $20,000 to replace the plastic windows with glass. This involved replacing the entire structure, since what we have is not strong enough to support glass. We are not interested in spending this much money, and would like to repair what we have. Your guidance in how to replace these windows would be greatly appreciated.

Welcome to the forums! It will be difficult for us to advise you to replace a bad situation with another one. So you will understand if we suggest you reframe the porch to where standard windows will fit the openings, then install the windows, finishing the outside and inside. The plastic you had before doubtfully was very water proof, so installing proper windows will enhance the house's value as well.
Of course, if you want to, post a few pictures on a site such as photobucket.com and copy/paste the HTML code to your reply post. That way we can see what you see.