Before going into locations of Regals I would ask the question if you are ready to take on such a finicky and difficult fish? What type of QT? Meds on hand? What other fish are in the tank you plan to place it? Do you have experience with angels?
That being said you can get some nice Pacific specimens out of Marshal, Fiji and Vanuatu. I think Indonesia is hit or miss, but if it is from LA then probalby good since they will most likely come from Quality Marine. The yellow belly is the Indian ocean variety and can come from not only the Red Sea.
Either way this is not an easy fish and should only be purchased if you are ready for it.