It might be useful to take a holiday in Thailand where you can get any pharmaceutical under the sun without a prescription! (The way it should be.) It's amazing how developing countries are much more advanced in this regard.

The funniest thing that I heard was when I was looking for distilled water. I found out it could be obtained with a prescription at a pharmacy. (This is according to the concierge type company that assists us in Japan; sometimes they come up with weird stuff and I am suspicious about this one.)

I then found that the best source of distilled (or possibly deionized water) is at auto-parts stores. The best price I found is 300 yen for 2 liters at Home's (in their tiny automotive section). Otherwise, Autobacs and Yellow Hat are the obvious sources.