Pack in back.
Blackburn's Barrier Small Seat Bag keeps you ready for the rigors of riding while keeping the elements out of your emergency gear. It's made with an abrasion-resistant waterproof material with welded seams and a weather-resistant zipper. Minimalist styling works on any bike, and hook-and-loop straps mount it to virtually any saddle and seatpost combination.
0.45 liter capacity. Claimed weight is 31 g. Features reflective accents for increased visibility.
What you need for a road ride.