I just bought this one off of Amazon a couple weeks ago.
http://www.amazon.com/Classic-Access...words=tank+bag
It's big enough to hold a gallon of milk (on it's side) and a little bit more stuff without using the expanding zipper. With the expansion zipper open it is quite large.
So far it is working pretty well. I did use the straps on each end, the magnets seem a little small. The straps have buickes up under the tank bag and are very quick to clip/unclip.
The craftsmanship is not perfect, there is a funny little pucker in the clear plastic window in the top right corner But for $42 and free shipping with my Amazon Prime I think it is worth it. Walmart sells the same tank bag on their web site for a few dollars more, but they have free shipping to your nearest walmart store if you don't have Amazon Prime it might be cheaper.
Wine and Dog food? you really know how to treat the ladies.