[Mr Gazza]

I was going to suggest the fat NVT grips that Stevie suggested, in a slightly jocular way!
I'm not sure they would look right on a Monster and not convinced that they did any good on my many big vibey Brit twins either.

I wouldn't bother filling the bars either. I filled one with lead once.. It didn't work!

As Darren points out, the modern answer is to tune out the vibes with bar end weights.

As for white finger, This is common and it may be that you suffer from Raynauds Syndrome?
I suffer from this without riding a bike, riding just brings it out! It's caused by temperature change and not so much from vibes.

My Doctor prescribed me Nifedipine and it works, as several Monster owners on here will tell you... Sometimes called the little red miracle pill... It's a game changer. No modification to the bike required.
Ask your GP.