But then you cannot grip the top of the bar behind where the Bag is..

In the past I took a used Strap on bag, Some what similar , added a stiffener panel some long bolts and spacers ..

and used a Handlebar mounted bottle cage adapter to put the bag on the bars with room behind it..

Safety pinned a Ball compass on the front of the bag..

The 'Valuables " were in a Money Belt Under my clothing..

Draping the largish OS paper map in a water resistant cover worked in the rain.





...