Here is where I buy all of my bags. They are 1 mil but they have a flap on them and they are 12x16. Same price.
http://store.storesupply.com/webapp/commerce/servlet/ProductDisplay?merchant_rn=631&prrfnbr=113581
http://store.storesupply.com/webapp/commerce/servlet/ProductDisplay?merchant_rn=631&prrfnbr=113581