I've just bought a WattWagon fat tire bike and I'm having trouble finding a bag that fits the rear rack. Specifically, most bag appear to use two long straps that fit across the rack at front and rear. Or I should say are supposed to fit... likely ok on a traditional rack, but much to short for a wide tire rack. I'm thinking four short straps, one at each corner is the way to go. Anyone have one in mind and care to share a link if possible?