This polycarbonate light diffuser was used in the bathroom on many 1970s Airstreams.
It is 20" tall and 3-7/8" wide. It is approximately 2" deep.
This diffuser is used on your original base. We do not sell the original base.
Although this is less likely to get melted or damaged due to the heat produced by incandescent light bulbs, we do suggest switching to LED bulbs to keep it cool and conserve battery power.