There is a company that makes and sells zip lock vacuum bags in different sizes for sous vide cooking. The bags have a valve in them that you place a hand pump over and suck all the air out of the bags. They get just as flat as the machine vacuum unit bags do. I have been using them for over a year and have not had a single problem. The beauty is that the bags can be washed and reused. The company is Asiani Candy Sous Vide kit. I was going to buy an electric vacuum sealer but now I don't have to. Link