Apologies for the lateness of the response, but if you're unable to get the CDs to support the series directly then I would recommend looking on Soundcloud & Bilibili. Several of the earlier songs are on SC, along with their sub-unit songs (rouge noir and sekai no uta) and their only full group song (swiiiiiitest party), whilst the last time I checked BB has their solo song series. Hope you find what you're looking for!
