A couple years ago I saw someone from the Rochester, MN Model A club that had made side curtains for their Roadster out of a sheet of clear plastic. This is the type of thick flexible plastic like the rear windows in older convertibles use. This was made as a temporary solution to not having side curtains. I liked it because it was cheap and quick to do, plus being all clear it didn't block the view out the side.
In the Twin Cities we have a surplus store called "The Axman", and when I was there yesterday they had some of this rolled up for $10 a roll. I bought a roll, and it's more than enough to do both sides of my Phaeton. They have a few more rolls, if someone in the area needs to make a good temporary, or even long term side curtains.