Can you guys recommend a simple, water-resistant backpack for under $40? Looking for something I could use to store my bottled water, keys, and maybe another thing or two - nothing over-the-top. Most of the stuff I've found online is either super expensive or when it's a bit less pricey, it comes with a ton of pockets and every bell and whistle under the sun. Wasn't sure where else to look, so figured I'd ask you guys. I'm assuming such a bag exists?