I was talking to a guy this week at VTR and he had a set of vinyl panels like Geo mentioned where it uses Lift-the-Dot connectors and connects at the front on the dash stud, then along the tonneau studs on the door, and then on the rear capping stud. He noted that a long stud is needed on the rear cap location. He did not have them installed but it appeared that they could be installed from outside the car except for the connector on the rear cap. He said they work great in conjunction with the wind wings in cold weather. I did not get the name of the company that made them for him, but I do recall he said the guy that made them has a shop real close to The Roadster Factory shop in Pennsylvania. He said someone in TRF probably could tell you the name and phone number.
They looked fairly easy to make, so making them yourself is an option. And the good part is that they use the Lift-the-Dot connectors which are not expensive. There is a really good fabric store here in Raleigh that sells vinyl intended for exterior use on boats so it is very waterproof. That would work very good for these. It is more expensive than interior vinyl but not a lot more, and it would not take much fabric to make the covers.
Regards,
Bob