I can only suggest, to try to locate the nose a little better.
Put the bike on the center stand. Remove the panniers.
make sure the rear wheel is clear of the ground.
Select first gear with the motor off.
Rock the rear wheel quickly rotational forwards and backwards.To see if you can hear any clunk
Keep one hand on the drive shaft cover. In order to feel for any vibrations etc.
Get a long screwdriver or a short piece of garden hose ,about a foot long and use that as a sort of stethoscope to hear if you can locate the proximity of the clunk noise whilst vigiouresly rocking the wheel back and forward.
You will probably do better if you have someone to help you.
You might be able to do the same listening test with the motor going and driving the rear wheel.
Let us know how you go.
If you can feel a lot of play or slack and you can hear a noise in the hub of the rear wheel when the motor is off and in gear. my first suspect would be something worn in the drive shaft or the drive splines in the rear wheel assembly have started to wear and are starting to chop out.
Hope this helps.
Cheers , Winston66,
Northampton Western Ausrtalia