Glass baking lid broke - what to substitute? The glass lid for my pyrex 10x10 baking dish broke. What can I substitute? Tin foil doesn't work -- nothing cooks!  Ideas?

Thank you.
One "hack" to try is to put a larger glass baking dish on top (e.g. 9"x13" over an 8"x8"). It is heavy enough to make a moderately decent seal.