The camping company Coleman also sells safety blankets made out of mylar for around $2.00 USD and it comes in a big sheet. I folded mine in half to make it thicker because its on the thinner side.
or you can do what i do and order 150 sqaure feet of mylar from ebay.. lol i got the role it was so big i had a hard time cutting it..ahaha.. they got smaller rolls too..