Utilize all that unused space inside your frame's main triangle with Lone Peak's rugged USA-made frame bag. Its 1000D nylon construction can withstand any kind of riding you can imagine, and the multiple Velcro attachment straps up above mean it stays good as a glued to your top tube. Behind the water-resistant YKK zipper, you can pack the large main compartment as tightly as you like because there's small zippered pocket on the left side to keep your most-frequented items.
Main compartment features a through-port for routing a hydration hose / headphone cable. Pack measures 20" x 7" x 2.5". 4.91 L cargo capacity. Claimed weight is 7 oz. Made in the USA. Lifetime warranty.
What you need for a road ride.