I need a cycling bag

Yesterday I went for a bike ride with my friend Paul out to MEC (Canadian equivalent of REI). Being Vancouver, it was barely sprinkling when we left, but ended up with more of a light rain by the time we reached our destination.


It made me realize that other than needing a more padded bike seat, I need a cycling backpack. I don't want a bannier or a handlebar bag as I prefer to have the weight stabilized on my back and not on my bike. So what would my ideal bag need?

• Small and light. I don't want to think twice about grabbing the bagwhen I go out cycling. It should be a no-brainer. That means I can't think that it is going to be a burden in any way.
• Hold my wallet, keys, and cell phone. Basic stuff in case I stop some place along the way.
• Snacks or a lunch. For those rides where you end up going quite a distance.
• Waterproof. It's Vancouver.
• Hold my water bottle. I have never had a hydration pack and don't see a need for it. I am fine with using my water bottle cage on my bike for while I am riding. I just need a place to stash the bottle when I get off the bike.
• Place to hold my bike repair kit. I currently have my repair kit in a saddle bag. For those rare occasions where I might not want this backpack, I will probably keep the kit in the saddle bag. But I can't leave the bag on my bike when I lock it up, so it needs enough room to hold the saddle bag.
• Place to clip my helmet. I don't want to have to hold on to it while I am inside somewhere and I would prefer not to leave it on my bike. This is especially useful if the place I lock up my bike is not covered and it's raining outside.
• Can hold a jacket. If I start to feel warm I want a place to stash my jacket easily.

Obviously these requirements are generic enough so that the bag could also be used for day hiking or around town stuff. So having a bag that can hold a wallet, cell phone, keys, small saddle bag, and a light jacket should not be hard. I am sure my knowledgeable girlfriend (who once worked at REI and Western Mountaineering and is into her jobs enough to read all the product literature) can help me find the right bag for me.