Local Coin Shops In Japan--Help Needed

My son will be spending a couple weeks in Japan during February 2013. He'll be staying in Atsugi (Kanto Province, s/w of Tokyo) and may be visiting either Tokyo or Yokohama.

If he can fit into his schedule, he may be able to visit a coin shop or two and buy a thing or two for me. My interest is collecting 1oz silver coins--mostly bullion, but also OK with low-end numismatic (i.e: not too costly) coins. The "1oz silver" (or close to it) is the important part.

My questions:
1. Are there any coin shops in those areas that anybody "in the know" would recommend?
2. Are there any specific coins (Japanese or anything from that "general area") that you would recommend he try to find?

Thanks in advance for your help.