Making amazake

[khashimoto]

Help! I am having a heck of a time trying to find "sake kasu" in or around Sioux Falls, South Dakota. I am willing to drive to nearby states or have it shipped to procure this item. I don't want the bottled version, or make the koji version - I am specifically looking for the sake lees. My mother made amazake when I was growing up in Hawaii and I'm on a mission to revive this tradition with my own family.
Any leads will be greatly appreciated. Thanks!