When I go on long trips I take a long a 1gallon Rotopax fuel cell. I purchased it when I owned my Triumph explorer as I didn’t find the fuel capacity that great for a bike that was designed to go off road where there are no fuel stations. Long story short I kept the system and adapted it to go on the Rocket. The metal bracket I purchased was what I used on the back of the explorer as I travel with soft luggage. You can see it mounted in the photo.
The beauty of this system is that it is expandable to suit your needs.