Where to buy nano sim cutter?

Hi, I just recently moved to Japan and have an unlocked iPhone 5. I was interested in getting a b-mobile SIM card but need to cut it down so that it'll fit in my iPhone. I was wondering if anyone knew of a place that sold a nano sim cutter and where sand paper can be bought. Thank you in advance :)!

Nobody has commented so I'll try and answer. I can't read Japanese so hopefully someone corrects me if I'm wrong!

Try Dospara
http://www.dospara.co.jp/5shopping/detail_parts.php?bg=6&br=167&sbr=55...

They have a shop in Yokohama
http://shop.dospara.co.jp/pc/yke/entry/128880

If that doesn't work searching for Nano SIM Cutter on google.co.jp should give you some results.

You can buy sim cutters on amazon.jp. They can be had cheaper on ebay, but the shipping times will be a lot longer.

Sandpaper can be purchased any home improvement store, DIY store or 100 yen store.

here's the link:

http://www.amazon.co.jp/s/ref=nb_sb_noss?__mk_ja_JP=%83J%83%5E%83J%83i...

Thank you for your replies everyone! I tried looking around Akihabara today but I guess since its so uncommon, its hard to find. I'm going to go ahead and order it off of Amazon :)!

I can confirm that sandpaper works to make nano sim out of micro sim from bmobile. I am using it right now. The only issue is that the microsims from bmobile are larger than the ones used in nano sims (the copper is larger), in my home country (Sweden) nanosims and microsims have the same copper form factor, the only difference is surrounding plastic.
Also, you don't want to use all the contact surfaces on the bmobile sim, they have more than my normal nanosim. I had to remove parts of the copper to make it fit correctly, careful not to remove any parts of the actual chip below. Best thing is if you can test the sim in an iPhone 4/4s to see which contact surfaces are used.