For those of you who use the space saver cup, I found that the plastic lid from a plastic folger's 11 oz coffee container snaps perfectly on the top. This can come in handy when re-constituting foods or even when you happen to store most of your kitchen inside. Snug fit and mostly watertight. I dunno. If you think it might suit you, try it out.

Also, if you like pasta (or anything else that needs to be strained) you can poke holes in the lid and it works really well.