When I go for longer trips, I bring my TengTools 1/4" socket set, which haven't seen much use.
Always brings 3,4,5,6mm allen keys and a Leatherman tool, a couple zipties and some tape. The 5mm is needed every time the seat's going on and off for the saddlebags. And needed the zip ties and leatherman when the hoses connecting the carb nipples started to pop off.
The spark plugs are 18mm, a Tengtools/Kamasa 18mm deep socket works ok. In Norway, 18mm spark plug wrenches are hard to find..
(As for the spark plugs : wonderin, should be possible to swap those NGK DPR plugs with NGK CPR plugs...? The threads are the same, only the CPR's are 16mm instead of 18mm hex diam. More room to work, and uses the same spark plug wrench as most jap bikes.