You might find it easier to skip the little water bottles and use a water bladder in a seat bag. An Outdoor Research water bladder is available at our local WalMart in the sporting goods section for about $10. Now for the slightly less ordinary... I found a Case Logic oxygen bottle carrier on clearance at my local drug store, and used that to put the water bladder in. It's just the right size, comes with its own straps, is padded (aka insulated), and has a drawstring closure to make removal of the water bladder easy. I think Hostel Shoppe and others also sell hydration bladders that may work for you. Here is a picture of my solution: