If you are not afraid of a bit of cutting, Cobra Company makes a conversion kit to build the Fujimi 1/48 AH-1J into an AH-1G. It includes a completely new doghouse, turret, cockpit, etc.
The Fujimi 1/48 AH-1J is a fine kit in itself. It is out of production, but they are not terribly hard to find on the forums or on ebay, if you are patient. I'd also recommend the Cobra Company AH-1J cockpit for it.