Is the buzz related to a certain engine RPM range?
A certain amount of harmonic vibration is normal in most engine designs.
If so just running with a higher or lower engine speed may help.
There are some relatively cheap handlebar grips out there that may help.
A quick way to try if that is heading in the right direction maybe something like this:
Check the sizing.
With my bike a VT750 ACE, a bike that vibrates worse than the VT500 due to crank design.
I chased down similar symptoms, trying various things.
I found in my case, the stock handlebars and the nerves or blood flow in my wrists didn't get along on longer rides and my hands would start to go numb and if they did I'd have a "pins and needles" sensation as they returned to normal.
I changed the angle of my handlebars in the clamps and noticed some relief, but not a complete solution, but it pointed me in the direction for my solution.
After some experimentation, sitting in the shed mocking up various positions with bicycle handlebars, electrical conduit, zip ties and duct tape to find where my hands felt most comfortable. I then took measurements and went handlebar hunting online.
I ended up switching to a different lower handlebar type with a different wrist angle and the problem went away.