The bathroom vanity light in my 1962
Tradewind was missing its shade. Searching around the forums shows people trying various materials to replace it. Here's what I did:
For the shade material, I used a sheet of 0.06" thick polyethylene from Amazon
, cut 18" x 6". This will bend the required 90 degrees over its 6-inch width, but takes a little bit of force.
When I first crammed it between the end plates of the fixture, it bowed down dramatically in the bottom center, which looked lousy. To fix this, I cut an 18" length of aluminum bar from Home Depot (1/8" x 1/2"). I stuck this in between the end caps with the lower edge of the shade resting on it. The result still bows very slightly, but warming the polyethylene puts it even further back into shape. The aluminum even makes a reasonably attractive lower border to the shade. You can see it, edge-on, in the photo.