I can find the catalog number of the cassette print only on the website Asahi Record (a CD shop).
Some people know if this website is reliable for the catalog numbers? I think it is, when I have the possibility to check the catalog number on other websites (like Oricon or Suruga-ya), the infos always correspond.
A link:
http://www.aaaa.co.jp/products/ANIME/ANIME/SA_1.html