I have been using dawia spool case in large size (first photo)
got them from fish head . it would cost about 30buck
which it hold two spool
Shimano SW18k, SW20k, FA SW16k(japan), yumeya 16k, FA20k, dawia dog fight 6500 and GT 6000
there is shimano spool case but i haven,t try them yet . might be the medium size ?
but i might check them out for my twinpower 8k and som 16k and stella SW10K
they all come in 3 size S,M,L