Are there any helicopters equipped with pressurized cabins?
Helicopter cabins are not usually pressurized as they are not expected to be operated at high altitudes.

The largest operational helicopter, the Mil Mi 26 Halo has a pressurized crew cabin. 

The Russian Mil Mi-24 Hind and Mil Mi 28 Havoc feature pressurized cockpits. However, these are for operating in an NBC environment, not for high altitude operation.