Originally Posted by BarnYardCamp
where can the 1/8 inch thick what ever it is be purchased?
Sorry, I just saw this. Here's one option, located here in Arizona:
It's just about $1 a square foot for the 1/8th inch thick version. I found no performance difference between the CeraTex product sold in the link above and the EHP Rollboard brand, which is about $2.25 a square foot and available from them here: https://engineheatprotection.com/prices/
Some of the forum members highly recommend a cheaper option in the form of 1/4-inch foam board. Home Depot used to carry it, but they don't seem to any longer. It was the Owens Corning Foamular brand. Somebody recently posted that Lowe's has one, the Kingspan version, but they are also showing it out of stock.