Cut two 8"x11" pieces of fabric (one from the fabric and one from the lining).
Also cut four 3" circles (two for the outside and two for the inside).
Make sure all pieces are well ironed.
On the 11" sides of the rectangle, iron 1/2" to the inside.
Fold the rectangle long ways, right sides facing.
Pin the circle to the end, with the wrong side showing.
Sew circle to the side of the bag. Repeat for the opposite side and the lining.
Turn Bag so the right side is out, and place the lining on the inside. Slide the zipper between the two layers and sew the first side.
Fold a long strip of fabric so no edges are showing, then sew into place. Cut into four pieces.
Sew velcro to the tips of each strip.
Sew two strips to the bottom of the bag. Place the other two between the fabric and lining. Add the zipper between the lining and strips of fabric.
Sew second side together.
Attach to Bike!