I found a soft side bag kit from Ducati. It mounts easily on the left side and works pretty well on my S2R for the commute to work. It would accomodate a couple changes of clothes I think but definitely not the tent or sleeping bag. Should be OK on a longer trip. The part number I have is 96740303BA.
For other bag ideas you might check out
www.aerostich.com. Their site is pretty deep so you may have to click around a bit, but I recall that they have a bunch of styles of bags.
Having done a number of long trips on various bikes, I don't know if I'd support the backpack idea. Those things get REALLY HEAVY after awhile.
Good luck.