looking for a ....

pressurized twin engine aircraft that would be great for sightseeing as well from the passenger point of view.. not mine as the pilot.

I'm thinking C337, not pressurized but would a charter company just have oxygen per individual?

I'm looking for something that I could tour the mountains above 12.5k mark and preferably offer twin engine reliability

maybe single engine is the way to go?

what would a real air charter company do in a case like this?

thanks