I have a single strap backpack that is fairly large, however i don't remember where i got it from. It would definitely be what you're looking for. It has thick durable nylon fabric with a waterproof lining. Larger front pocket has a full double zipper (up over, and back down), and the zipper pulls on main compartment AND the front pocket have holes you can use to secure them with a key ring or lock. It has loops on the very front you can hook things to, and clips on either side to keep the strain off the zipper when full, as well as some mesh pockets for small items (pack of gum etc). I use it to go grocery shopping and pretty much anything else that won't fit in a large pocket. The part against the back is padded too. I will dig around and see if i can't find same/similar online for you......
- Andy
Last edited by TransitBiker; 04-20-14 at 01:02 AM.