The Wiilie & Max Take Along bag had a bracket mount and fits very neatly under the dashboard on the passenger
side.

http://www.westendmotorsports.com/willie-take-along-windshield-bags-large-p-12802.html

I used velcro to initially mount the bracket intending to bolt it on once I had the positioning correct - but 2 yeas on it's still just velcro'd on and works fine!

Red Leader drive