The online site I have order from are:
Akadot
Japan Amazon
The Amazon is hard to search since it is in Japanese, so hope you have someone that can read Japanese. ^^: I have Niki help me search of them. hehehhe

Artbook:
Much Ado About Nothing ISBN4-901926-35-7

The Comedy of Errors ISBN4-901923-77-2

Manga:

Mythical Detective Loki 1 ISBN4-7575-0070-X

Mythical Detective Loki 2 ISBN4-7575-0208-7

Mythical Detective Loki 3 ISBN4-7575-0258-3

Mythical Detective Loki 4 ISBN4-7575-0345-8

Mythical Detective Loki 5 ISBN4-7575-0421-7

Mythical Detective Loki 6 ISBN4-7575-0535-3

Mythical Detective Loki 7 ISBN4-7575-0594-9

Mythical Detective Loki Ragnarok 1 ISBN4-901926-16-0

Mythical Detective Loki Ragnarok 2 ISBN4-901926-39-X

Mythical Detective Loki Ragnarok 3 ISBN4-901926-80-2