The first place I know of to get it in America is through eBay.com Online Auctions. You can usually find the soundtracks available, but, if you are lucky, you can also find the games themselves. Yahoo! Auctions has been known to have the soundtracks available, as well. Check them out sometime.

IMPORTERS!!!
I would like to thank Enig for giving me this information.

You can buy the Games at "National Console Support"

You can buy the Original Soundtracks at "CD Japan"

Also, to get the last information on the Original Soundtracks, go here: http://www.konami.co.jp/kme/index.html