I was looking for the same thing but found small nylon lightweight dry bags to be a good alternative. I wish there was a better concept for closing the bag without using the buckle.

I am currently using a Exped (http://www.exped.com) XXS Fold-Drybag. Its a bit on the large size (1 litre - 6"x5"x3"), but the beauty of dry bags is that you can fold down the opening as much as you can thus decreasing the size of the bag. I know I probably didn't explain it right, but if your not familiar with dry bags you'll see its self explanatory from the pictures.

Kris
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"One should not increase, beyond what is necessary, the number of entities required to explain anything"
William of Ockham (1285-1349)