It isn't fun being out late 30 miles from home and hitting reserve.
Ya' think?
For those of us with roadworthy machines...that get ridden real distances...it's arguably the #1 buzzkill. At this time, there's no clean & painless method for adding fuel capacity. I started out by researching various ways to increase range and quickly found that every last one of them involves at least one big compromise. You didn't think that I
liked that 1-gallon gas can on the rear rack, did you!
It was just zero work, dirt cheap, and viable...fugly, too.
At this late date, I have mixed feeling about the rear rack, too. That said, if you want to do some real riding, form follows function. If it were to plan a seriously long road trip, the rear rack would go back on the bike, the auxiliary tank, too....even if that meant the old 1-gallon can.
Seems to me that your best-fit solution is going to boil down to a choice between the fuel bladders scooter mentioned and a hard tank, of some type. IDK, if an extra liter will do the job for you, maybe it's time to source a G`Craft side tank and be done with it.