Thank you for the advice.
I've already checked out Amazon-Japan. I can't find the items I'm looking for and most of the shops on Amazon-Japan do not ship to the United Kingdom.
I think my best bet is to find someone living in Japan who can find some bottled water that has been sourced in those prefectures, then send them out to me here. However, after some research, its seems you can only buy Aichi bottled water, in Aichi. Places like airports etc. It doesn't look like you'd find Kanagawa bottled water, in Tokyo for example. So I understand it might be a pain, even for someone living in Japan, to locate and buy what I'm looking for.
It's a total stretch I know. I'm designing and creating some Kitsune masks for an art project. The need for the water is purely symbolic and not essential. It would not make a difference to the look of the finished pieces, but it's the idea behind it that's important. The water will be used to make a glue. The glue will then be the very substance that binds the whole creation together. The idea that the essence of that glue is made from water from those prefectures is very symbolic. It would be a nice story to tell, as the masks will be a unique project and will be given away as gifts.
Proving to be very difficult to make this a reality!
I appreciate you helping out, though!