Water resistant, or water proof?

Take a look at bicycle commuting backpacks. This banjo brothers is economical but probably not your style. My friend has a chrome bag like this that she really digs. Timbuktu make a retty big one and a smaller one.

I don't know of any backpacks that really embody the look you might be going for, while staying waterproof. I guess they all end up being a bit urban/techwear. You could also look at MFA's suggestions - either the everlane snap or the whole suggestion list here