I did a trip to White Island in 1997 about a year before I moved from Gisborne to Wairarapa.
It was with a company called Vulcan Helicopters, but I don't think they exist any more.
We flew out there in a Hughes 500, four of us plus the pilot.
It was an amazing trip, but I got the feeling it could potentially be a very dangerous place and the air was full of sulphur fumes.