I need silver Samurai for C.C my Sophie.

Eastern quests are little tough on me to clear with 3 stars to get Samurai.

so I been tryinh 2k summon for.. around 500k gold so far..

no luck ..

Alissa x 2
Daiela x 1
Harissa x 3
Cecily x 1
Giovanni x 1
Calliope x 1
Verotte x 1
Percis x 1

I am really sure I got almost every silver I can get from 2k summon
do samurai even drop this way ?
I do have quite of S.C as well, should I just wait for next month and roll Premium summon?

I actually spent 150 S.C this month and still have not gotten single silver samurai...