I think you need to let people know they may have to search through all of the above retailers stock to find the made in Japan discs.
I've seen Sony, Fuji and Maxell discs that say they are from Taiwan. Something else I forgot to mention, was that I've had several sales people tell me who work at these stores is that they pull the made from Japan discs and substitute the made from Taiwan discs when a sale is going on. Supposedly, they do have to pay more for the made from Japan discs and would rather have the unsuspecting public buy the made from Taiwan discs when a sale is going on. I've found this to be the case more than once when the sale is over than the premium stuff comes back out.
You just have to be careful and check.