Look to the right of your screen and there are several supply houses with web sites for coldframes and greenhouses and supplies. I often use recycled materials or clear painters drop clothes doubled so there is a dead air space. I wrap it around the lid frame. Cheap. Does it work as well as some of these plastics? I dunno but what I use seems to do fine.

Thanks...How silly that they are right in front of my face!
Thanks for the heads up!

Just read in a Garden Hints book to use bubble wrap - that stuff that is sold for packages!

Try Peaceful Valley.It may not be too far from you.

Here is a link that might be useful: Peaceful Valley

The local furniture store will have big pieces of plastic that go around mattresses for free.

Mama's right! Mattress stores are great places to scavenge large pieces of plastic. I even found a hugmongous piece of king size bubble wrap, doubled and sewn together 3 sides.