Unfortunately, I did not have much luck in finding a supplier for you :-(!
But I did find two individuals trading in obscure and hard to find Japanese classics and some Japan produced music CD's by well known musical groups.
Note: Japan based
Note: Not based in Japan
I'm sorry this isn't much. Most of what I found are already trading in Ebay so pricing might be an issue that's why I did not include them. Please do note that, this two individuals trade on such specialized genre's of Japanese produced DVD's that it may take a bit of negotiations to convince them to sell to you wholesale. And because they are not considered as an established business, please do take the precaution of doing extra research and asking as many question as possible.
If you need help looking up other suppliers for other products, feel free to post them on the forum. We'll be happy to assist you :-)!