I used to get them at Berkeley Bowl, but now they are on Amazon! They have so much more flavor than the typical rice cracker (but if you eat them exclusively, your tongue will go numb). They’re great to add to a mix though.
New cracker discovery — distinctly more Japanese seeming: crunchy and delicious. Just fed one to the guy sitting next to me and he reports “It tastes like a bento box. Like tempura and all that.” Adding to my mix!
For a mix, I don’t think you can do better than the kind that comes in a can:
(fair warning that it has wheat flour in the list of ingredients)