We've found that a regular shower curtain very nicely covers both walls. You have to trim it a little vertically, and then some horizontally so that it's not at your feet. We attached it to the wall with large velcro dots, and they have held great so far for 6 months. We've been in temps down in the teens, but nothing real hot yet.
When you are packing up, you simply fold the walls as usual, and the curtain just folds with it. Very convenient, and WAY better than OEM. A regular polyester shower curtain covers the wall above the shower controls, and the open space you walk through to get into the tub.
Dave