Hi Rusty,
As a small replacement for zip-lock bags I have used many different sizes of "Whirl-pak bags. They are plastic bags that have 2 thin wires (kind of like 2 twist ties) across the opening. You close the bag like you would a large fold-top dry bag. I think somewhere it the past on the ETS site there was a omparison of them with Gerber milk bags.
I have sealed liquid in them many times and they are quite tough.
Mike