These plastic doohickies might look like shower caps, but they are actually designed to protect food. Just slip them over plates, platters or any other container, and you have a food-preserving cover. Many of the companies that make them use breathable plastic to maintain moisture without spoilage.
We like these simple and reusable covers for a number of reasons. First, the safety of most plastic leftover containers is suspect; these allow you to use your chemically stable ceramic and glass dishes and containers. Next, using plastic wrap is often as cumbersome as it is wasteful; how many times have you wrapped and re-wrapped a dish only to have a pretty crummy seal? Last, these covers turn the containers we already have into food storage. (As a bonus, they’d probably make adequate shower caps).
There are a number of manufactures offering these covers on Amazon. Most are under $15 and include several sizes for various containers.