Board Thread:General Discussion/@comment-34828117-20180226130342/@comment-32233739-20180301120529

every now and again there is also an elderkai banner where you just get elderkais (nothing else on the banner) so that can be a good source

and there are lots of story events that have elder kais in baba shop for the currency from there event (i.e. kachi kachin, metal fruits etc) so keep an eye out for them

you will get them eventually :)