The Ruthworks Randonneur is an updated, lightweight, durable, and user friendly iteration of the traditional handlebar bag.
This bag requires a rack support and I recommend something similar to the Velo Orange Flat Pack Rack.
Front Envelope pocket
Two rear Envelope pockets
Two flat side pockets
Full sized map case
Bottom velcro straps
Bottom anchor point
Tombstone sleeve that fits Nitto, Velo Orange, Soma, Compass, and other randonneur racks.
Inside sorting pockets
Includes two straps for attachment to the handlebars