Help: Looking for Good Dog Walking Bag

We recently moved to an area with a LOT more green space than our previous apartment. In the old place, I'd keep a milk crate outside our front door with Sadie's toys, and use the Chuck It* at the end of the street. If we did go somewhere, I'd just pack it up in a back pack, take Sadie to a field, and have fun.

Seriously. Best outdoor toy made for dogs who love fetch, and human shoulders that can't throw.

But now, I'll take the 2 dogs for a walk around the neighborhood, stop at the green space, and play with Sadie and let Zep just sniff around, pee on things, and grunt. The problem is with two dogs, getting the toys out of the back pack off of my shoulder is cumbersome and awkward. I also have this moment of panic each time I take the bag off that I dropped a leash. It's a worse feeling than those nightmares where you think you lost all of your teeth, or show up to school naked.

I tried a tote bag for easy access, but I keep loosing my keys at the bottom of the bag. So I switched to one of the cheap drawstring backpacks, but the straps keep falling down over my shoulders, when the toy is in use.

So what do you use for walks/exercise with your dogs when you're out walking? Dog walkers, what do you use that is convenient, lightweight and durable? Ideally, something that would fit a Chuck It, water bottle/collapsible bowl, and has a place for slobbery tennis balls? I'd love some feedback!