Fizik Medium Seat Bag
Fizik's Saddle Pak is the perfect companion for carrying your ride essentials. This water-resistant bag sports a reflective safety patch and a taillight attachment loop.
I love this bag. I have used it on my mountain bike for the last 4 years. I have the same complaint of the top zipper, as with it being waterproof it makes it harder to open. I find that its a two hand job to do. But other than that, it carrys just enough for me. Keys, multitool, tire levers, the compact towels PP sells, and room for other stuff. Phones, etc.
Only complaint would be the zipper being on top. This makes it hard to open. I would like the zipper to be on the bottom.