A lot of vibrations can be cured very easily with soft sided velcro.In the past i've used it on the fairing shield, fairing infill trays and also used it to reinforce plastics that have started to crack due to age like the triangular panels that sit just under the seat on both sides.It has a very strong sticky side that doesn't budge and is very inconspicuous.Double check your engine mounting bolts are correctly tightened, and not cracked at all as this can be a major cause for extra vibes, and make sure your centre stand and exhaust aren't rattling away on each other.As mentioned, indicators as well as wing mirror glass have been known to be culprits in the past as well.
Maybe carbs need balancing?
Not sure about shoving foam under the fuel tank as a fix for a buzzing vibration, it could/would eventually get water logged (Rain or washing) and cause ignition/electrical and rusting problems, especially to the base of the tank.It already has some black foamy shit already on the underside of the tank looks o.e. as well, i meant i would maybe try and get some newer stuff as you can see when you lift up the tank it's work down in certain places.
Worn front tyre in the shape of a triangle ?